Merge remote-tracking branch 'kwolf/for-anthony' into staging

* kwolf/for-anthony: (38 commits)
  qemu-iotests: Fix test 031 for qcow2 v3 support
  qemu-iotests: Add -o and make v3 the default for qcow2
  qcow2: Zero write support
  qemu-iotests: Test backing file COW with zero clusters
  qemu-iotests: add a simple test for write_zeroes
  qcow2: Support for feature table header extension
  qcow2: Support reading zero clusters
  qcow2: Version 3 images
  qcow2: Ignore reserved bits in check_refcounts
  qcow2: Ignore reserved bits in refcount table entries
  qcow2: Simplify count_cow_clusters
  qcow2: Refactor qcow2_free_any_clusters
  qcow2: Ignore reserved bits in L1/L2 entries
  qcow2: Fail write_compressed when overwriting data
  qcow2: Ignore reserved bits in count_contiguous_clusters()
  qcow2: Ignore reserved bits in get_cluster_offset
  qcow2: Save disk size in snapshot header
  Specification for qcow2 version 3
  qcow2: Fix refcount block allocation during qcow2_alloc_cluster_at()
  iotests: Resolve test failures caused by hostname
  ...

50 files changed, 1704 insertions, 567 deletions

diff --git a/aio.c b/aio.c
index eb3bf42..0a9eb10 100644
--- a/aio.c
+++ b/aio.c
@@ -35,7 +35,6 @@ struct AioHandler
     IOHandler *io_read;
     IOHandler *io_write;
     AioFlushHandler *io_flush;
-    AioProcessQueue *io_process_queue;
     int deleted;
     void *opaque;
     QLIST_ENTRY(AioHandler) node;
@@ -58,7 +57,6 @@ int qemu_aio_set_fd_handler(int fd,
                             IOHandler *io_read,
                             IOHandler *io_write,
                             AioFlushHandler *io_flush,
-                            AioProcessQueue *io_process_queue,
                             void *opaque)
 {
     AioHandler *node;
@@ -91,7 +89,6 @@ int qemu_aio_set_fd_handler(int fd,
         node->io_read = io_read;
         node->io_write = io_write;
         node->io_flush = io_flush;
-        node->io_process_queue = io_process_queue;
         node->opaque = opaque;
     }
 
@@ -102,131 +99,96 @@ int qemu_aio_set_fd_handler(int fd,
 
 void qemu_aio_flush(void)
 {
-    AioHandler *node;
-    int ret;
-
-    do {
-        ret = 0;
-
-	/*
-	 * If there are pending emulated aio start them now so flush
-	 * will be able to return 1.
-	 */
-        qemu_aio_wait();
-
-        QLIST_FOREACH(node, &aio_handlers, node) {
-            if (node->io_flush) {
-                ret |= node->io_flush(node->opaque);
-            }
-        }
-    } while (qemu_bh_poll() || ret > 0);
+    while (qemu_aio_wait());
 }
 
-int qemu_aio_process_queue(void)
+bool qemu_aio_wait(void)
 {
     AioHandler *node;
-    int ret = 0;
+    fd_set rdfds, wrfds;
+    int max_fd = -1;
+    int ret;
+    bool busy;
+
+    /*
+     * If there are callbacks left that have been queued, we need to call then.
+     * Do not call select in this case, because it is possible that the caller
+     * does not need a complete flush (as is the case for qemu_aio_wait loops).
+     */
+    if (qemu_bh_poll()) {
+        return true;
+    }
 
     walking_handlers = 1;
 
+    FD_ZERO(&rdfds);
+    FD_ZERO(&wrfds);
+
+    /* fill fd sets */
+    busy = false;
     QLIST_FOREACH(node, &aio_handlers, node) {
-        if (node->io_process_queue) {
-            if (node->io_process_queue(node->opaque)) {
-                ret = 1;
+        /* If there aren't pending AIO operations, don't invoke callbacks.
+         * Otherwise, if there are no AIO requests, qemu_aio_wait() would
+         * wait indefinitely.
+         */
+        if (node->io_flush) {
+            if (node->io_flush(node->opaque) == 0) {
+                continue;
             }
+            busy = true;
+        }
+        if (!node->deleted && node->io_read) {
+            FD_SET(node->fd, &rdfds);
+            max_fd = MAX(max_fd, node->fd + 1);
+        }
+        if (!node->deleted && node->io_write) {
+            FD_SET(node->fd, &wrfds);
+            max_fd = MAX(max_fd, node->fd + 1);
         }
     }
 
     walking_handlers = 0;
 
-    return ret;
-}
-
-void qemu_aio_wait(void)
-{
-    int ret;
-
-    if (qemu_bh_poll())
-        return;
-
-    /*
-     * If there are callbacks left that have been queued, we need to call then.
-     * Return afterwards to avoid waiting needlessly in select().
-     */
-    if (qemu_aio_process_queue())
-        return;
+    /* No AIO operations?  Get us out of here */
+    if (!busy) {
+        return false;
+    }
 
-    do {
-        AioHandler *node;
-        fd_set rdfds, wrfds;
-        int max_fd = -1;
+    /* wait until next event */
+    ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);
 
+    /* if we have any readable fds, dispatch event */
+    if (ret > 0) {
         walking_handlers = 1;
 
-        FD_ZERO(&rdfds);
-        FD_ZERO(&wrfds);
+        /* we have to walk very carefully in case
+         * qemu_aio_set_fd_handler is called while we're walking */
+        node = QLIST_FIRST(&aio_handlers);
+        while (node) {
+            AioHandler *tmp;
 
-        /* fill fd sets */
-        QLIST_FOREACH(node, &aio_handlers, node) {
-            /* If there aren't pending AIO operations, don't invoke callbacks.
-             * Otherwise, if there are no AIO requests, qemu_aio_wait() would
-             * wait indefinitely.
-             */
-            if (node->io_flush && node->io_flush(node->opaque) == 0)
-                continue;
-
-            if (!node->deleted && node->io_read) {
-                FD_SET(node->fd, &rdfds);
-                max_fd = MAX(max_fd, node->fd + 1);
+            if (!node->deleted &&
+                FD_ISSET(node->fd, &rdfds) &&
+                node->io_read) {
+                node->io_read(node->opaque);
             }
-            if (!node->deleted && node->io_write) {
-                FD_SET(node->fd, &wrfds);
-                max_fd = MAX(max_fd, node->fd + 1);
+            if (!node->deleted &&
+                FD_ISSET(node->fd, &wrfds) &&
+                node->io_write) {
+                node->io_write(node->opaque);
             }
-        }
 
-        walking_handlers = 0;
+            tmp = node;
+            node = QLIST_NEXT(node, node);
 
-        /* No AIO operations?  Get us out of here */
-        if (max_fd == -1)
-            break;
-
-        /* wait until next event */
-        ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);
-        if (ret == -1 && errno == EINTR)
-            continue;
-
-        /* if we have any readable fds, dispatch event */
-        if (ret > 0) {
-            walking_handlers = 1;
-
-            /* we have to walk very carefully in case
-             * qemu_aio_set_fd_handler is called while we're walking */
-            node = QLIST_FIRST(&aio_handlers);
-            while (node) {
-                AioHandler *tmp;
-
-                if (!node->deleted &&
-                    FD_ISSET(node->fd, &rdfds) &&
-                    node->io_read) {
-                    node->io_read(node->opaque);
-                }
-                if (!node->deleted &&
-                    FD_ISSET(node->fd, &wrfds) &&
-                    node->io_write) {
-                    node->io_write(node->opaque);
-                }
-
-                tmp = node;
-                node = QLIST_NEXT(node, node);
-
-                if (tmp->deleted) {
-                    QLIST_REMOVE(tmp, node);
-                    g_free(tmp);
-                }
+            if (tmp->deleted) {
+                QLIST_REMOVE(tmp, node);
+                g_free(tmp);
             }
-
-            walking_handlers = 0;
         }
-    } while (ret == 0);
+
+        walking_handlers = 0;
+    }
+
+    return true;
 }
diff --git a/block.c b/block.c
index c0c90f0..fe74ddd 100644
--- a/block.c
+++ b/block.c
@@ -80,6 +80,8 @@ static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
                                                void *opaque,
                                                bool is_write);
 static void coroutine_fn bdrv_co_do_rw(void *opaque);
+static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors);
 
 static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
         bool is_write, double elapsed_time, uint64_t *wait);
@@ -812,10 +814,13 @@ unlink_and_fail:
 
 void bdrv_close(BlockDriverState *bs)
 {
+    bdrv_flush(bs);
     if (bs->drv) {
         if (bs->job) {
             block_job_cancel_sync(bs->job);
         }
+        bdrv_drain_all();
+
         if (bs == bs_snapshots) {
             bs_snapshots = NULL;
         }
@@ -1705,8 +1710,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
 
     if (drv->bdrv_co_write_zeroes &&
         buffer_is_zero(bounce_buffer, iov.iov_len)) {
-        ret = drv->bdrv_co_write_zeroes(bs, cluster_sector_num,
-                                        cluster_nb_sectors);
+        ret = bdrv_co_do_write_zeroes(bs, cluster_sector_num,
+                                      cluster_nb_sectors);
     } else {
         ret = drv->bdrv_co_writev(bs, cluster_sector_num, cluster_nb_sectors,
                                   &bounce_qiov);
@@ -1816,9 +1821,15 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
     struct iovec iov;
     int ret;
 
+    /* TODO Emulate only part of misaligned requests instead of letting block
+     * drivers return -ENOTSUP and emulate everything */
+
     /* First try the efficient write zeroes operation */
     if (drv->bdrv_co_write_zeroes) {
-        return drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
+        ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
+        if (ret != -ENOTSUP) {
+            return ret;
+        }
     }
 
     /* Fall back to bounce buffer if write zeroes is unsupported */
diff --git a/block/cow.c b/block/cow.c
index 8d3c9f8..a5a00eb 100644
--- a/block/cow.c
+++ b/block/cow.c
@@ -103,7 +103,7 @@ static int cow_open(BlockDriverState *bs, int flags)
 }
 
 /*
- * XXX(hch): right now these functions are extremely ineffcient.
+ * XXX(hch): right now these functions are extremely inefficient.
  * We should just read the whole bitmap we'll need in one go instead.
  */
 static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
diff --git a/block/curl.c b/block/curl.c
index a909eca..bf3680b 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -89,19 +89,17 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
     DPRINTF("CURL (AIO): Sock action %d on fd %d\n", action, fd);
     switch (action) {
         case CURL_POLL_IN:
-            qemu_aio_set_fd_handler(fd, curl_multi_do, NULL, curl_aio_flush,
-                                    NULL, s);
+            qemu_aio_set_fd_handler(fd, curl_multi_do, NULL, curl_aio_flush, s);
             break;
         case CURL_POLL_OUT:
-            qemu_aio_set_fd_handler(fd, NULL, curl_multi_do, curl_aio_flush,
-                                    NULL, s);
+            qemu_aio_set_fd_handler(fd, NULL, curl_multi_do, curl_aio_flush, s);
             break;
         case CURL_POLL_INOUT:
             qemu_aio_set_fd_handler(fd, curl_multi_do, curl_multi_do,
-                                    curl_aio_flush, NULL, s);
+                                    curl_aio_flush, s);
             break;
         case CURL_POLL_REMOVE:
-            qemu_aio_set_fd_handler(fd, NULL, NULL, NULL, NULL, NULL);
+            qemu_aio_set_fd_handler(fd, NULL, NULL, NULL, NULL);
             break;
     }
 
diff --git a/block/iscsi.c b/block/iscsi.c
index bd3ca11..5222726 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -108,7 +108,7 @@ iscsi_set_events(IscsiLun *iscsilun)
     qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), iscsi_process_read,
                            (iscsi_which_events(iscsi) & POLLOUT)
                            ? iscsi_process_write : NULL,
-                           iscsi_process_flush, NULL, iscsilun);
+                           iscsi_process_flush, iscsilun);
 }
 
 static void
@@ -682,7 +682,7 @@ static void iscsi_close(BlockDriverState *bs)
     IscsiLun *iscsilun = bs->opaque;
     struct iscsi_context *iscsi = iscsilun->iscsi;
 
-    qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), NULL, NULL, NULL, NULL, NULL);
+    qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), NULL, NULL, NULL, NULL);
     iscsi_destroy_context(iscsi);
     memset(iscsilun, 0, sizeof(IscsiLun));
 }
diff --git a/block/nbd.c b/block/nbd.c
index e0af5b4..56dbf6e 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -203,7 +203,7 @@ static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,
     qemu_co_mutex_lock(&s->send_mutex);
     s->send_coroutine = qemu_coroutine_self();
     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write,
-                            nbd_have_request, NULL, s);
+                            nbd_have_request, s);
     rc = nbd_send_request(s->sock, request);
     if (rc >= 0 && iov) {
         ret = qemu_co_sendv(s->sock, iov, request->len, offset);
@@ -212,7 +212,7 @@ static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,
         }
     }
     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL,
-                            nbd_have_request, NULL, s);
+                            nbd_have_request, s);
     s->send_coroutine = NULL;
     qemu_co_mutex_unlock(&s->send_mutex);
     return rc;
@@ -285,7 +285,7 @@ static int nbd_establish_connection(BlockDriverState *bs)
      * kick the reply mechanism.  */
     socket_set_nonblock(sock);
     qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL,
-                            nbd_have_request, NULL, s);
+                            nbd_have_request, s);
 
     s->sock = sock;
     s->size = size;
@@ -305,7 +305,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
     request.len = 0;
     nbd_send_request(s->sock, &request);
 
-    qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL, NULL);
+    qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL);
     closesocket(s->sock);
 }
 
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index cbd224d..a747a88 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -195,7 +195,7 @@ static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
 
     l2_table = *table;
 
-    if (old_l2_offset == 0) {
+    if ((old_l2_offset & L1E_OFFSET_MASK) == 0) {
         /* if there was no old l2 table, clear the new table */
         memset(l2_table, 0, s->l2_size * sizeof(uint64_t));
     } else {
@@ -203,7 +203,8 @@ static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
 
         /* if there was an old l2 table, read it from the disk */
         BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_COW_READ);
-        ret = qcow2_cache_get(bs, s->l2_table_cache, old_l2_offset,
+        ret = qcow2_cache_get(bs, s->l2_table_cache,
+            old_l2_offset & L1E_OFFSET_MASK,
             (void**) &old_table);
         if (ret < 0) {
             goto fail;
@@ -246,28 +247,44 @@ fail:
     return ret;
 }
 
+/*
+ * Checks how many clusters in a given L2 table are contiguous in the image
+ * file. As soon as one of the flags in the bitmask stop_flags changes compared
+ * to the first cluster, the search is stopped and the cluster is not counted
+ * as contiguous. (This allows it, for example, to stop at the first compressed
+ * cluster which may require a different handling)
+ */
 static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
-        uint64_t *l2_table, uint64_t start, uint64_t mask)
+        uint64_t *l2_table, uint64_t start, uint64_t stop_flags)
 {
     int i;
-    uint64_t offset = be64_to_cpu(l2_table[0]) & ~mask;
+    uint64_t mask = stop_flags | L2E_OFFSET_MASK;
+    uint64_t offset = be64_to_cpu(l2_table[0]) & mask;
 
     if (!offset)
         return 0;
 
-    for (i = start; i < start + nb_clusters; i++)
-        if (offset + (uint64_t) i * cluster_size != (be64_to_cpu(l2_table[i]) & ~mask))
+    for (i = start; i < start + nb_clusters; i++) {
+        uint64_t l2_entry = be64_to_cpu(l2_table[i]) & mask;
+        if (offset + (uint64_t) i * cluster_size != l2_entry) {
             break;
+        }
+    }
 
 	return (i - start);
 }
 
 static int count_contiguous_free_clusters(uint64_t nb_clusters, uint64_t *l2_table)
 {
-    int i = 0;
+    int i;
+
+    for (i = 0; i < nb_clusters; i++) {
+        int type = qcow2_get_cluster_type(be64_to_cpu(l2_table[i]));
 
-    while(nb_clusters-- && l2_table[i] == 0)
-        i++;
+        if (type != QCOW2_CLUSTER_UNALLOCATED) {
+            break;
+        }
+    }
 
     return i;
 }
@@ -367,11 +384,9 @@ out:
  *
  * on exit, *num is the number of contiguous sectors we can read.
  *
- * Return 0, if the offset is found
- * Return -errno, otherwise.
- *
+ * Returns the cluster type (QCOW2_CLUSTER_*) on success, -errno in error
+ * cases.
  */
-
 int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
     int *num, uint64_t *cluster_offset)
 {
@@ -407,19 +422,19 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
     /* seek the the l2 offset in the l1 table */
 
     l1_index = offset >> l1_bits;
-    if (l1_index >= s->l1_size)
+    if (l1_index >= s->l1_size) {
+        ret = QCOW2_CLUSTER_UNALLOCATED;
         goto out;
+    }
 
-    l2_offset = s->l1_table[l1_index];
-
-    /* seek the l2 table of the given l2 offset */
-
-    if (!l2_offset)
+    l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
+    if (!l2_offset) {
+        ret = QCOW2_CLUSTER_UNALLOCATED;
         goto out;
+    }
 
     /* load the l2 table in memory */
 
-    l2_offset &= ~QCOW_OFLAG_COPIED;
     ret = l2_load(bs, l2_offset, &l2_table);
     if (ret < 0) {
         return ret;
@@ -431,26 +446,44 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
     *cluster_offset = be64_to_cpu(l2_table[l2_index]);
     nb_clusters = size_to_clusters(s, nb_needed << 9);
 
-    if (!*cluster_offset) {
+    ret = qcow2_get_cluster_type(*cluster_offset);
+    switch (ret) {
+    case QCOW2_CLUSTER_COMPRESSED:
+        /* Compressed clusters can only be processed one by one */
+        c = 1;
+        *cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK;
+        break;
+    case QCOW2_CLUSTER_ZERO:
+        c = count_contiguous_clusters(nb_clusters, s->cluster_size,
+                &l2_table[l2_index], 0,
+                QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
+        *cluster_offset = 0;
+        break;
+    case QCOW2_CLUSTER_UNALLOCATED:
         /* how many empty clusters ? */
         c = count_contiguous_free_clusters(nb_clusters, &l2_table[l2_index]);
-    } else {
+        *cluster_offset = 0;
+        break;
+    case QCOW2_CLUSTER_NORMAL:
         /* how many allocated clusters ? */
         c = count_contiguous_clusters(nb_clusters, s->cluster_size,
-                &l2_table[l2_index], 0, QCOW_OFLAG_COPIED);
+                &l2_table[l2_index], 0,
+                QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
+        *cluster_offset &= L2E_OFFSET_MASK;
+        break;
     }
 
     qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
 
-   nb_available = (c * s->cluster_sectors);
+    nb_available = (c * s->cluster_sectors);
+
 out:
     if (nb_available > nb_needed)
         nb_available = nb_needed;
 
     *num = nb_available - index_in_cluster;
 
-    *cluster_offset &=~QCOW_OFLAG_COPIED;
-    return 0;
+    return ret;
 }
 
 /*
@@ -483,13 +516,13 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
             return ret;
         }
     }
-    l2_offset = s->l1_table[l1_index];
+
+    l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
 
     /* seek the l2 table of the given l2 offset */
 
-    if (l2_offset & QCOW_OFLAG_COPIED) {
+    if (s->l1_table[l1_index] & QCOW_OFLAG_COPIED) {
         /* load the l2 table in memory */
-        l2_offset &= ~QCOW_OFLAG_COPIED;
         ret = l2_load(bs, l2_offset, &l2_table);
         if (ret < 0) {
             return ret;
@@ -505,7 +538,7 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
         if (l2_offset) {
             qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
         }
-        l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;
+        l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
     }
 
     /* find the cluster offset for the given disk offset */
@@ -546,15 +579,14 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
         return 0;
     }
 
+    /* Compression can't overwrite anything. Fail if the cluster was already
+     * allocated. */
     cluster_offset = be64_to_cpu(l2_table[l2_index]);
-    if (cluster_offset & QCOW_OFLAG_COPIED) {
+    if (cluster_offset & L2E_OFFSET_MASK) {
         qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
         return 0;
     }
 
-    if (cluster_offset)
-        qcow2_free_any_clusters(bs, cluster_offset, 1);
-
     cluster_offset = qcow2_alloc_bytes(bs, compressed_size);
     if (cluster_offset < 0) {
         qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
@@ -663,8 +695,7 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
      */
     if (j != 0) {
         for (i = 0; i < j; i++) {
-            qcow2_free_any_clusters(bs,
-                be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED, 1);
+            qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1);
         }
     }
 
@@ -682,29 +713,28 @@ err:
 static int count_cow_clusters(BDRVQcowState *s, int nb_clusters,
     uint64_t *l2_table, int l2_index)
 {
-    int i = 0;
-    uint64_t cluster_offset;
+    int i;
 
-    while (i < nb_clusters) {
-        i += count_contiguous_clusters(nb_clusters - i, s->cluster_size,
-                &l2_table[l2_index], i, 0);
-        if ((i >= nb_clusters) || be64_to_cpu(l2_table[l2_index + i])) {
-            break;
-        }
+    for (i = 0; i < nb_clusters; i++) {
+        uint64_t l2_entry = be64_to_cpu(l2_table[l2_index + i]);
+        int cluster_type = qcow2_get_cluster_type(l2_entry);
 
-        i += count_contiguous_free_clusters(nb_clusters - i,
-                &l2_table[l2_index + i]);
-        if (i >= nb_clusters) {
+        switch(cluster_type) {
+        case QCOW2_CLUSTER_NORMAL:
+            if (l2_entry & QCOW_OFLAG_COPIED) {
+                goto out;
+            }
             break;
-        }
-
-        cluster_offset = be64_to_cpu(l2_table[l2_index + i]);
-
-        if ((cluster_offset & QCOW_OFLAG_COPIED) ||
-                (cluster_offset & QCOW_OFLAG_COMPRESSED))
+        case QCOW2_CLUSTER_UNALLOCATED:
+        case QCOW2_CLUSTER_COMPRESSED:
+        case QCOW2_CLUSTER_ZERO:
             break;
+        default:
+            abort();
+        }
     }
 
+out:
     assert(i <= nb_clusters);
     return i;
 }
@@ -842,10 +872,14 @@ again:
      * Check how many clusters are already allocated and don't need COW, and how
      * many need a new allocation.
      */
-    if (cluster_offset & QCOW_OFLAG_COPIED) {
+    if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL
+        && (cluster_offset & QCOW_OFLAG_COPIED))
+    {
         /* We keep all QCOW_OFLAG_COPIED clusters */
-        keep_clusters = count_contiguous_clusters(nb_clusters, s->cluster_size,
-                                                  &l2_table[l2_index], 0, 0);
+        keep_clusters =
+            count_contiguous_clusters(nb_clusters, s->cluster_size,
+                                      &l2_table[l2_index], 0,
+                                      QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO);
         assert(keep_clusters <= nb_clusters);
         nb_clusters -= keep_clusters;
     } else {
@@ -860,7 +894,7 @@ again:
         cluster_offset = 0;
     }
 
-    cluster_offset &= ~QCOW_OFLAG_COPIED;
+    cluster_offset &= L2E_OFFSET_MASK;
 
     /* If there is something left to allocate, do that now */
     *m = (QCowL2Meta) {
@@ -931,7 +965,7 @@ again:
 fail:
     qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
 fail_put:
-    if (nb_clusters > 0) {
+    if (m->nb_clusters > 0) {
         QLIST_REMOVE(m, next_in_flight);
     }
     return ret;
@@ -1015,9 +1049,7 @@ static int discard_single_l2(BlockDriverState *bs, uint64_t offset,
         uint64_t old_offset;
 
         old_offset = be64_to_cpu(l2_table[l2_index + i]);
-        old_offset &= ~QCOW_OFLAG_COPIED;
-
-        if (old_offset == 0) {
+        if ((old_offset & L2E_OFFSET_MASK) == 0) {
             continue;
         }
 
@@ -1070,3 +1102,75 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
 
     return 0;
 }
+
+/*
+ * This zeroes as many clusters of nb_clusters as possible at once (i.e.
+ * all clusters in the same L2 table) and returns the number of zeroed
+ * clusters.
+ */
+static int zero_single_l2(BlockDriverState *bs, uint64_t offset,
+    unsigned int nb_clusters)
+{
+    BDRVQcowState *s = bs->opaque;
+    uint64_t *l2_table;
+    int l2_index;
+    int ret;
+    int i;
+
+    ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
+    if (ret < 0) {
+        return ret;
+    }
+
+    /* Limit nb_clusters to one L2 table */
+    nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
+
+    for (i = 0; i < nb_clusters; i++) {
+        uint64_t old_offset;
+
+        old_offset = be64_to_cpu(l2_table[l2_index + i]);
+
+        /* Update L2 entries */
+        qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
+        if (old_offset & QCOW_OFLAG_COMPRESSED) {
+            l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO);
+            qcow2_free_any_clusters(bs, old_offset, 1);
+        } else {
+            l2_table[l2_index + i] |= cpu_to_be64(QCOW_OFLAG_ZERO);
+        }
+    }
+
+    ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return nb_clusters;
+}
+
+int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors)
+{
+    BDRVQcowState *s = bs->opaque;
+    unsigned int nb_clusters;
+    int ret;
+
+    /* The zero flag is only supported by version 3 and newer */
+    if (s->qcow_version < 3) {
+        return -ENOTSUP;
+    }
+
+    /* Each L2 table is handled by its own loop iteration */
+    nb_clusters = size_to_clusters(s, nb_sectors << BDRV_SECTOR_BITS);
+
+    while (nb_clusters > 0) {
+        ret = zero_single_l2(bs, offset, nb_clusters);
+        if (ret < 0) {
+            return ret;
+        }
+
+        nb_clusters -= ret;
+        offset += (ret * s->cluster_size);
+    }
+
+    return 0;
+}
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index f39928a..812c93c 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -167,7 +167,7 @@ static int alloc_refcount_block(BlockDriverState *bs,
     if (refcount_table_index < s->refcount_table_size) {
 
         uint64_t refcount_block_offset =
-            s->refcount_table[refcount_table_index];
+            s->refcount_table[refcount_table_index] & REFT_OFFSET_MASK;
 
         /* If it's already there, we're done */
         if (refcount_block_offset) {
@@ -400,7 +400,7 @@ static int alloc_refcount_block(BlockDriverState *bs,
         return ret;
     }
 
-    return new_block;
+    return 0;
 
 fail_table:
     g_free(new_table);
@@ -587,6 +587,7 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t cluster_index;
+    uint64_t old_free_cluster_index;
     int i, refcount, ret;
 
     /* Check how many clusters there are free */
@@ -602,11 +603,16 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
     }
 
     /* And then allocate them */
+    old_free_cluster_index = s->free_cluster_index;
+    s->free_cluster_index = cluster_index + i;
+
     ret = update_refcount(bs, offset, i << s->cluster_bits, 1);
     if (ret < 0) {
         return ret;
     }
 
+    s->free_cluster_index = old_free_cluster_index;
+
     return i;
 }
 
@@ -673,32 +679,35 @@ void qcow2_free_clusters(BlockDriverState *bs,
 }
 
 /*
- * free_any_clusters
- *
- * free clusters according to its type: compressed or not
- *
+ * Free a cluster using its L2 entry (handles clusters of all types, e.g.
+ * normal cluster, compressed cluster, etc.)
  */
-
 void qcow2_free_any_clusters(BlockDriverState *bs,
-    uint64_t cluster_offset, int nb_clusters)
+    uint64_t l2_entry, int nb_clusters)
 {
     BDRVQcowState *s = bs->opaque;
 
-    /* free the cluster */
-
-    if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
-        int nb_csectors;
-        nb_csectors = ((cluster_offset >> s->csize_shift) &
-                       s->csize_mask) + 1;
-        qcow2_free_clusters(bs,
-            (cluster_offset & s->cluster_offset_mask) & ~511,
-            nb_csectors * 512);
-        return;
+    switch (qcow2_get_cluster_type(l2_entry)) {
+    case QCOW2_CLUSTER_COMPRESSED:
+        {
+            int nb_csectors;
+            nb_csectors = ((l2_entry >> s->csize_shift) &
+                           s->csize_mask) + 1;
+            qcow2_free_clusters(bs,
+                (l2_entry & s->cluster_offset_mask) & ~511,
+                nb_csectors * 512);
+        }
+        break;
+    case QCOW2_CLUSTER_NORMAL:
+        qcow2_free_clusters(bs, l2_entry & L2E_OFFSET_MASK,
+                            nb_clusters << s->cluster_bits);
+        break;
+    case QCOW2_CLUSTER_UNALLOCATED:
+    case QCOW2_CLUSTER_ZERO:
+        break;
+    default:
+        abort();
     }
-
-    qcow2_free_clusters(bs, cluster_offset, nb_clusters << s->cluster_bits);
-
-    return;
 }
 
 
@@ -758,7 +767,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
         l2_offset = l1_table[i];
         if (l2_offset) {
             old_l2_offset = l2_offset;
-            l2_offset &= ~QCOW_OFLAG_COPIED;
+            l2_offset &= L1E_OFFSET_MASK;
 
             ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
                 (void**) &l2_table);
@@ -790,10 +799,11 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
                         /* compressed clusters are never modified */
                         refcount = 2;
                     } else {
+                        uint64_t cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits;
                         if (addend != 0) {
-                            refcount = update_cluster_refcount(bs, offset >> s->cluster_bits, addend);
+                            refcount = update_cluster_refcount(bs, cluster_index, addend);
                         } else {
-                            refcount = get_refcount(bs, offset >> s->cluster_bits);
+                            refcount = get_refcount(bs, cluster_index);
                         }
 
                         if (refcount < 0) {
@@ -931,7 +941,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
     int check_copied)
 {
     BDRVQcowState *s = bs->opaque;
-    uint64_t *l2_table, offset;
+    uint64_t *l2_table, l2_entry;
     int i, l2_size, nb_csectors, refcount;
 
     /* Read L2 table from disk */
@@ -943,54 +953,70 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
 
     /* Do the actual checks */
     for(i = 0; i < s->l2_size; i++) {
-        offset = be64_to_cpu(l2_table[i]);
-        if (offset != 0) {
-            if (offset & QCOW_OFLAG_COMPRESSED) {
-                /* Compressed clusters don't have QCOW_OFLAG_COPIED */
-                if (offset & QCOW_OFLAG_COPIED) {
-                    fprintf(stderr, "ERROR: cluster %" PRId64 ": "
-                        "copied flag must never be set for compressed "
-                        "clusters\n", offset >> s->cluster_bits);
-                    offset &= ~QCOW_OFLAG_COPIED;
-                    res->corruptions++;
-                }
+        l2_entry = be64_to_cpu(l2_table[i]);
+
+        switch (qcow2_get_cluster_type(l2_entry)) {
+        case QCOW2_CLUSTER_COMPRESSED:
+            /* Compressed clusters don't have QCOW_OFLAG_COPIED */
+            if (l2_entry & QCOW_OFLAG_COPIED) {
+                fprintf(stderr, "ERROR: cluster %" PRId64 ": "
+                    "copied flag must never be set for compressed "
+                    "clusters\n", l2_entry >> s->cluster_bits);
+                l2_entry &= ~QCOW_OFLAG_COPIED;
+                res->corruptions++;
+            }
 
-                /* Mark cluster as used */
-                nb_csectors = ((offset >> s->csize_shift) &
-                               s->csize_mask) + 1;
-                offset &= s->cluster_offset_mask;
-                inc_refcounts(bs, res, refcount_table, refcount_table_size,
-                    offset & ~511, nb_csectors * 512);
-            } else {
-                /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
-                if (check_copied) {
-                    uint64_t entry = offset;
-                    offset &= ~QCOW_OFLAG_COPIED;
-                    refcount = get_refcount(bs, offset >> s->cluster_bits);
-                    if (refcount < 0) {
-                        fprintf(stderr, "Can't get refcount for offset %"
-                            PRIx64 ": %s\n", entry, strerror(-refcount));
-                        goto fail;
-                    }
-                    if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {
-                        fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
-                            PRIx64 " refcount=%d\n", entry, refcount);
-                        res->corruptions++;
-                    }
-                }
+            /* Mark cluster as used */
+            nb_csectors = ((l2_entry >> s->csize_shift) &
+                           s->csize_mask) + 1;
+            l2_entry &= s->cluster_offset_mask;
+            inc_refcounts(bs, res, refcount_table, refcount_table_size,
+                l2_entry & ~511, nb_csectors * 512);
+            break;
 
-                /* Mark cluster as used */
-                offset &= ~QCOW_OFLAG_COPIED;
-                inc_refcounts(bs, res, refcount_table,refcount_table_size,
-                    offset, s->cluster_size);
+        case QCOW2_CLUSTER_ZERO:
+            if ((l2_entry & L2E_OFFSET_MASK) == 0) {
+                break;
+            }
+            /* fall through */
 
-                /* Correct offsets are cluster aligned */
-                if (offset & (s->cluster_size - 1)) {
-                    fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
-                        "properly aligned; L2 entry corrupted.\n", offset);
+        case QCOW2_CLUSTER_NORMAL:
+        {
+            /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
+            uint64_t offset = l2_entry & L2E_OFFSET_MASK;
+
+            if (check_copied) {
+                refcount = get_refcount(bs, offset >> s->cluster_bits);
+                if (refcount < 0) {
+                    fprintf(stderr, "Can't get refcount for offset %"
+                        PRIx64 ": %s\n", l2_entry, strerror(-refcount));
+                    goto fail;
+                }
+                if ((refcount == 1) != ((l2_entry & QCOW_OFLAG_COPIED) != 0)) {
+                    fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
+                        PRIx64 " refcount=%d\n", l2_entry, refcount);
                     res->corruptions++;
                 }
             }
+
+            /* Mark cluster as used */
+            inc_refcounts(bs, res, refcount_table,refcount_table_size,
+                offset, s->cluster_size);
+
+            /* Correct offsets are cluster aligned */
+            if (offset & (s->cluster_size - 1)) {
+                fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
+                    "properly aligned; L2 entry corrupted.\n", offset);
+                res->corruptions++;
+            }
+            break;
+        }
+
+        case QCOW2_CLUSTER_UNALLOCATED:
+            break;
+
+        default:
+            abort();
         }
     }
 
@@ -1061,7 +1087,7 @@ static int check_refcounts_l1(BlockDriverState *bs,
             }
 
             /* Mark L2 table as used */
-            l2_offset &= ~QCOW_OFLAG_COPIED;
+            l2_offset &= L1E_OFFSET_MASK;
             inc_refcounts(bs, res, refcount_table, refcount_table_size,
                 l2_offset, s->cluster_size);
 
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 7d3fde5..42f971b 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -48,6 +48,7 @@ typedef struct QEMU_PACKED QCowSnapshotHeader {
 
 typedef struct QEMU_PACKED QCowSnapshotExtraData {
     uint64_t vm_state_size_large;
+    uint64_t disk_size;
 } QCowSnapshotExtraData;
 
 void qcow2_free_snapshots(BlockDriverState *bs)
@@ -117,6 +118,12 @@ int qcow2_read_snapshots(BlockDriverState *bs)
             sn->vm_state_size = be64_to_cpu(extra.vm_state_size_large);
         }
 
+        if (extra_data_size >= 16) {
+            sn->disk_size = be64_to_cpu(extra.disk_size);
+        } else {
+            sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
+        }
+
         /* Read snapshot ID */
         sn->id_str = g_malloc(id_str_size + 1);
         ret = bdrv_pread(bs->file, offset, sn->id_str, id_str_size);
@@ -197,6 +204,7 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
 
         memset(&extra, 0, sizeof(extra));
         extra.vm_state_size_large = cpu_to_be64(sn->vm_state_size);
+        extra.disk_size = cpu_to_be64(sn->disk_size);
 
         id_str_size = strlen(sn->id_str);
         name_size = strlen(sn->name);
@@ -330,6 +338,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
     sn->id_str = g_strdup(sn_info->id_str);
     sn->name = g_strdup(sn_info->name);
 
+    sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
     sn->vm_state_size = sn_info->vm_state_size;
     sn->date_sec = sn_info->date_sec;
     sn->date_nsec = sn_info->date_nsec;
@@ -426,6 +435,13 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
     }
     sn = &s->snapshots[snapshot_index];
 
+    if (sn->disk_size != bs->total_sectors * BDRV_SECTOR_SIZE) {
+        error_report("qcow2: Loading snapshots with different disk "
+            "size is not implemented");
+        ret = -ENOTSUP;
+        goto fail;
+    }
+
     /*
      * Make sure that the current L1 table is big enough to contain the whole
      * L1 table of the snapshot. If the snapshot L1 table is smaller, the
diff --git a/block/qcow2.c b/block/qcow2.c
index 70d3141..ad46c03 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -54,6 +54,7 @@ typedef struct {
 } QCowExtension;
 #define  QCOW2_EXT_MAGIC_END 0
 #define  QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
+#define  QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
 
 static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
@@ -61,7 +62,7 @@ static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
 
     if (buf_size >= sizeof(QCowHeader) &&
         be32_to_cpu(cow_header->magic) == QCOW_MAGIC &&
-        be32_to_cpu(cow_header->version) >= QCOW_VERSION)
+        be32_to_cpu(cow_header->version) >= 2)
         return 100;
     else
         return 0;
@@ -76,7 +77,7 @@ static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
  * return 0 upon success, non-0 otherwise
  */
 static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
-                                 uint64_t end_offset)
+                                 uint64_t end_offset, void **p_feature_table)
 {
     BDRVQcowState *s = bs->opaque;
     QCowExtension ext;
@@ -134,6 +135,18 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
 #endif
             break;
 
+        case QCOW2_EXT_MAGIC_FEATURE_TABLE:
+            if (p_feature_table != NULL) {
+                void* feature_table = g_malloc0(ext.len + 2 * sizeof(Qcow2Feature));
+                ret = bdrv_pread(bs->file, offset , feature_table, ext.len);
+                if (ret < 0) {
+                    return ret;
+                }
+
+                *p_feature_table = feature_table;
+            }
+            break;
+
         default:
             /* unknown magic - save it in case we need to rewrite the header */
             {
@@ -169,6 +182,37 @@ static void cleanup_unknown_header_ext(BlockDriverState *bs)
     }
 }
 
+static void report_unsupported(BlockDriverState *bs, const char *fmt, ...)
+{
+    char msg[64];
+    va_list ap;
+
+    va_start(ap, fmt);
+    vsnprintf(msg, sizeof(msg), fmt, ap);
+    va_end(ap);
+
+    qerror_report(QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
+        bs->device_name, "qcow2", msg);
+}
+
+static void report_unsupported_feature(BlockDriverState *bs,
+    Qcow2Feature *table, uint64_t mask)
+{
+    while (table && table->name[0] != '\0') {
+        if (table->type == QCOW2_FEAT_TYPE_INCOMPATIBLE) {
+            if (mask & (1 << table->bit)) {
+                report_unsupported(bs, "%.46s",table->name);
+                mask &= ~(1 << table->bit);
+            }
+        }
+        table++;
+    }
+
+    if (mask) {
+        report_unsupported(bs, "Unknown incompatible feature: %" PRIx64, mask);
+    }
+}
+
 static int qcow2_open(BlockDriverState *bs, int flags)
 {
     BDRVQcowState *s = bs->opaque;
@@ -199,14 +243,73 @@ static int qcow2_open(BlockDriverState *bs, int flags)
         ret = -EINVAL;
         goto fail;
     }
-    if (header.version != QCOW_VERSION) {
-        char version[64];
-        snprintf(version, sizeof(version), "QCOW version %d", header.version);
-        qerror_report(QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
-            bs->device_name, "qcow2", version);
+    if (header.version < 2 || header.version > 3) {
+        report_unsupported(bs, "QCOW version %d", header.version);
+        ret = -ENOTSUP;
+        goto fail;
+    }
+
+    s->qcow_version = header.version;
+
+    /* Initialise version 3 header fields */
+    if (header.version == 2) {
+        header.incompatible_features    = 0;
+        header.compatible_features      = 0;
+        header.autoclear_features       = 0;
+        header.refcount_order           = 4;
+        header.header_length            = 72;
+    } else {
+        be64_to_cpus(&header.incompatible_features);
+        be64_to_cpus(&header.compatible_features);
+        be64_to_cpus(&header.autoclear_features);
+        be32_to_cpus(&header.refcount_order);
+        be32_to_cpus(&header.header_length);
+    }
+
+    if (header.header_length > sizeof(header)) {
+        s->unknown_header_fields_size = header.header_length - sizeof(header);
+        s->unknown_header_fields = g_malloc(s->unknown_header_fields_size);
+        ret = bdrv_pread(bs->file, sizeof(header), s->unknown_header_fields,
+                         s->unknown_header_fields_size);
+        if (ret < 0) {
+            goto fail;
+        }
+    }
+
+    if (header.backing_file_offset) {
+        ext_end = header.backing_file_offset;
+    } else {
+        ext_end = 1 << header.cluster_bits;
+    }
+
+    /* Handle feature bits */
+    s->incompatible_features    = header.incompatible_features;
+    s->compatible_features      = header.compatible_features;
+    s->autoclear_features       = header.autoclear_features;
+
+    if (s->incompatible_features != 0) {
+        void *feature_table = NULL;
+        qcow2_read_extensions(bs, header.header_length, ext_end,
+                              &feature_table);
+        report_unsupported_feature(bs, feature_table,
+                                   s->incompatible_features);
+        ret = -ENOTSUP;
+        goto fail;
+    }
+
+    if (!bs->read_only && s->autoclear_features != 0) {
+        s->autoclear_features = 0;
+        qcow2_update_header(bs);
+    }
+
+    /* Check support for various header values */
+    if (header.refcount_order != 4) {
+        report_unsupported(bs, "%d bit reference counts",
+                           1 << header.refcount_order);
         ret = -ENOTSUP;
         goto fail;
     }
+
     if (header.cluster_bits < MIN_CLUSTER_BITS ||
         header.cluster_bits > MAX_CLUSTER_BITS) {
         ret = -EINVAL;
@@ -280,12 +383,7 @@ static int qcow2_open(BlockDriverState *bs, int flags)
     QLIST_INIT(&s->cluster_allocs);
 
     /* read qcow2 extensions */
-    if (header.backing_file_offset) {
-        ext_end = header.backing_file_offset;
-    } else {
-        ext_end = s->cluster_size;
-    }
-    if (qcow2_read_extensions(bs, sizeof(header), ext_end)) {
+    if (qcow2_read_extensions(bs, header.header_length, ext_end, NULL)) {
         ret = -EINVAL;
         goto fail;
     }
@@ -321,6 +419,7 @@ static int qcow2_open(BlockDriverState *bs, int flags)
     return ret;
 
  fail:
+    g_free(s->unknown_header_fields);
     cleanup_unknown_header_ext(bs);
     qcow2_free_snapshots(bs);
     qcow2_refcount_close(bs);
@@ -449,7 +548,8 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
         qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
             cur_nr_sectors * 512);
 
-        if (!cluster_offset) {
+        switch (ret) {
+        case QCOW2_CLUSTER_UNALLOCATED:
 
             if (bs->backing_hd) {
                 /* read from the base image */
@@ -469,7 +569,17 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
                 /* Note: in this case, no need to wait */
                 qemu_iovec_memset(&hd_qiov, 0, 512 * cur_nr_sectors);
             }
-        } else if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
+            break;
+
+        case QCOW2_CLUSTER_ZERO:
+            if (s->qcow_version < 3) {
+                ret = -EIO;
+                goto fail;
+            }
+            qemu_iovec_memset(&hd_qiov, 0, 512 * cur_nr_sectors);
+            break;
+
+        case QCOW2_CLUSTER_COMPRESSED:
             /* add AIO support for compressed blocks ? */
             ret = qcow2_decompress_cluster(bs, cluster_offset);
             if (ret < 0) {
@@ -479,7 +589,9 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
             qemu_iovec_from_buffer(&hd_qiov,
                 s->cluster_cache + index_in_cluster * 512,
                 512 * cur_nr_sectors);
-        } else {
+            break;
+
+        case QCOW2_CLUSTER_NORMAL:
             if ((cluster_offset & 511) != 0) {
                 ret = -EIO;
                 goto fail;
@@ -520,6 +632,12 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
                 qemu_iovec_from_buffer(&hd_qiov, cluster_data,
                     512 * cur_nr_sectors);
             }
+            break;
+
+        default:
+            g_assert_not_reached();
+            ret = -EIO;
+            goto fail;
         }
 
         remaining_sectors -= cur_nr_sectors;
@@ -671,7 +789,9 @@ static void qcow2_close(BlockDriverState *bs)
     qcow2_cache_destroy(bs, s->l2_table_cache);
     qcow2_cache_destroy(bs, s->refcount_block_cache);
 
+    g_free(s->unknown_header_fields);
     cleanup_unknown_header_ext(bs);
+
     g_free(s->cluster_cache);
     qemu_vfree(s->cluster_data);
     qcow2_refcount_close(bs);
@@ -745,10 +865,10 @@ int qcow2_update_header(BlockDriverState *bs)
     int ret;
     uint64_t total_size;
     uint32_t refcount_table_clusters;
+    size_t header_length;
     Qcow2UnknownHeaderExtension *uext;
 
     buf = qemu_blockalign(bs, buflen);
-    memset(buf, 0, s->cluster_size);
 
     /* Header structure */
     header = (QCowHeader*) buf;
@@ -758,12 +878,14 @@ int qcow2_update_header(BlockDriverState *bs)
         goto fail;
     }
 
+    header_length = sizeof(*header) + s->unknown_header_fields_size;
     total_size = bs->total_sectors * BDRV_SECTOR_SIZE;
     refcount_table_clusters = s->refcount_table_size >> (s->cluster_bits - 3);
 
     *header = (QCowHeader) {
+        /* Version 2 fields */
         .magic                  = cpu_to_be32(QCOW_MAGIC),
-        .version                = cpu_to_be32(QCOW_VERSION),
+        .version                = cpu_to_be32(s->qcow_version),
         .backing_file_offset    = 0,
         .backing_file_size      = 0,
         .cluster_bits           = cpu_to_be32(s->cluster_bits),
@@ -775,10 +897,42 @@ int qcow2_update_header(BlockDriverState *bs)
         .refcount_table_clusters = cpu_to_be32(refcount_table_clusters),
         .nb_snapshots           = cpu_to_be32(s->nb_snapshots),
         .snapshots_offset       = cpu_to_be64(s->snapshots_offset),
+
+        /* Version 3 fields */
+        .incompatible_features  = cpu_to_be64(s->incompatible_features),
+        .compatible_features    = cpu_to_be64(s->compatible_features),
+        .autoclear_features     = cpu_to_be64(s->autoclear_features),
+        .refcount_order         = cpu_to_be32(3 + REFCOUNT_SHIFT),
+        .header_length          = cpu_to_be32(header_length),
     };
 
-    buf += sizeof(*header);
-    buflen -= sizeof(*header);
+    /* For older versions, write a shorter header */
+    switch (s->qcow_version) {
+    case 2:
+        ret = offsetof(QCowHeader, incompatible_features);
+        break;
+    case 3:
+        ret = sizeof(*header);
+        break;
+    default:
+        return -EINVAL;
+    }
+
+    buf += ret;
+    buflen -= ret;
+    memset(buf, 0, buflen);
+
+    /* Preserve any unknown field in the header */
+    if (s->unknown_header_fields_size) {
+        if (buflen < s->unknown_header_fields_size) {
+            ret = -ENOSPC;
+            goto fail;
+        }
+
+        memcpy(buf, s->unknown_header_fields, s->unknown_header_fields_size);
+        buf += s->unknown_header_fields_size;
+        buflen -= s->unknown_header_fields_size;
+    }
 
     /* Backing file format header extension */
     if (*bs->backing_format) {
@@ -793,6 +947,19 @@ int qcow2_update_header(BlockDriverState *bs)
         buflen -= ret;
     }
 
+    /* Feature table */
+    Qcow2Feature features[] = {
+        /* no feature defined yet */
+    };
+
+    ret = header_ext_add(buf, QCOW2_EXT_MAGIC_FEATURE_TABLE,
+                         features, sizeof(features), buflen);
+    if (ret < 0) {
+        goto fail;
+    }
+    buf += ret;
+    buflen -= ret;
+
     /* Keep unknown header extensions */
     QLIST_FOREACH(uext, &s->unknown_header_ext, next) {
         ret = header_ext_add(buf, uext->magic, uext->data, uext->len, buflen);
@@ -910,7 +1077,7 @@ static int preallocate(BlockDriverState *bs)
 static int qcow2_create2(const char *filename, int64_t total_size,
                          const char *backing_file, const char *backing_format,
                          int flags, size_t cluster_size, int prealloc,
-                         QEMUOptionParameter *options)
+                         QEMUOptionParameter *options, int version)
 {
     /* Calculate cluster_bits */
     int cluster_bits;
@@ -954,13 +1121,15 @@ static int qcow2_create2(const char *filename, int64_t total_size,
     /* Write the header */
     memset(&header, 0, sizeof(header));
     header.magic = cpu_to_be32(QCOW_MAGIC);
-    header.version = cpu_to_be32(QCOW_VERSION);
+    header.version = cpu_to_be32(version);
     header.cluster_bits = cpu_to_be32(cluster_bits);
     header.size = cpu_to_be64(0);
     header.l1_table_offset = cpu_to_be64(0);
     header.l1_size = cpu_to_be32(0);
     header.refcount_table_offset = cpu_to_be64(cluster_size);
     header.refcount_table_clusters = cpu_to_be32(1);
+    header.refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT);
+    header.header_length = cpu_to_be32(sizeof(header));
 
     if (flags & BLOCK_FLAG_ENCRYPT) {
         header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
@@ -1042,6 +1211,7 @@ static int qcow2_create(const char *filename, QEMUOptionParameter *options)
     int flags = 0;
     size_t cluster_size = DEFAULT_CLUSTER_SIZE;
     int prealloc = 0;
+    int version = 2;
 
     /* Read out options */
     while (options && options->name) {
@@ -1067,6 +1237,16 @@ static int qcow2_create(const char *filename, QEMUOptionParameter *options)
                     options->value.s);
                 return -EINVAL;
             }
+        } else if (!strcmp(options->name, BLOCK_OPT_COMPAT_LEVEL)) {
+            if (!options->value.s || !strcmp(options->value.s, "0.10")) {
+                version = 2;
+            } else if (!strcmp(options->value.s, "1.1")) {
+                version = 3;
+            } else {
+                fprintf(stderr, "Invalid compatibility level: '%s'\n",
+                    options->value.s);
+                return -EINVAL;
+            }
         }
         options++;
     }
@@ -1078,7 +1258,7 @@ static int qcow2_create(const char *filename, QEMUOptionParameter *options)
     }
 
     return qcow2_create2(filename, sectors, backing_file, backing_fmt, flags,
-                         cluster_size, prealloc, options);
+                         cluster_size, prealloc, options, version);
 }
 
 static int qcow2_make_empty(BlockDriverState *bs)
@@ -1101,6 +1281,26 @@ static int qcow2_make_empty(BlockDriverState *bs)
     return 0;
 }
 
+static coroutine_fn int qcow2_co_write_zeroes(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors)
+{
+    int ret;
+    BDRVQcowState *s = bs->opaque;
+
+    /* Emulate misaligned zero writes */
+    if (sector_num % s->cluster_sectors || nb_sectors % s->cluster_sectors) {
+        return -ENOTSUP;
+    }
+
+    /* Whatever is left can use real zero clusters */
+    qemu_co_mutex_lock(&s->lock);
+    ret = qcow2_zero_clusters(bs, sector_num << BDRV_SECTOR_BITS,
+        nb_sectors);
+    qemu_co_mutex_unlock(&s->lock);
+
+    return ret;
+}
+
 static coroutine_fn int qcow2_co_discard(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors)
 {
@@ -1330,6 +1530,11 @@ static QEMUOptionParameter qcow2_create_options[] = {
         .help = "Virtual disk size"
     },
     {
+        .name = BLOCK_OPT_COMPAT_LEVEL,
+        .type = OPT_STRING,
+        .help = "Compatibility level (0.10 or 1.1)"
+    },
+    {
         .name = BLOCK_OPT_BACKING_FILE,
         .type = OPT_STRING,
         .help = "File name of a base image"
@@ -1373,6 +1578,7 @@ static BlockDriver bdrv_qcow2 = {
     .bdrv_co_writev         = qcow2_co_writev,
     .bdrv_co_flush_to_os    = qcow2_co_flush_to_os,
 
+    .bdrv_co_write_zeroes   = qcow2_co_write_zeroes,
     .bdrv_co_discard        = qcow2_co_discard,
     .bdrv_truncate          = qcow2_truncate,
     .bdrv_write_compressed  = qcow2_write_compressed,
diff --git a/block/qcow2.h b/block/qcow2.h
index e4ac366..93567f6 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -33,7 +33,6 @@
 //#define DEBUG_EXT
 
 #define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
-#define QCOW_VERSION 2
 
 #define QCOW_CRYPT_NONE 0
 #define QCOW_CRYPT_AES  1
@@ -44,6 +43,8 @@
 #define QCOW_OFLAG_COPIED     (1LL << 63)
 /* indicate that the cluster is compressed (they never have the copied flag) */
 #define QCOW_OFLAG_COMPRESSED (1LL << 62)
+/* The cluster reads as all zeros */
+#define QCOW_OFLAG_ZERO (1LL << 0)
 
 #define REFCOUNT_SHIFT 1 /* refcount size is 2 bytes */
 
@@ -71,6 +72,14 @@ typedef struct QCowHeader {
     uint32_t refcount_table_clusters;
     uint32_t nb_snapshots;
     uint64_t snapshots_offset;
+
+    /* The following fields are only valid for version >= 3 */
+    uint64_t incompatible_features;
+    uint64_t compatible_features;
+    uint64_t autoclear_features;
+
+    uint32_t refcount_order;
+    uint32_t header_length;
 } QCowHeader;
 
 typedef struct QCowSnapshot {
@@ -78,6 +87,7 @@ typedef struct QCowSnapshot {
     uint32_t l1_size;
     char *id_str;
     char *name;
+    uint64_t disk_size;
     uint64_t vm_state_size;
     uint32_t date_sec;
     uint32_t date_nsec;
@@ -94,6 +104,18 @@ typedef struct Qcow2UnknownHeaderExtension {
     uint8_t data[];
 } Qcow2UnknownHeaderExtension;
 
+enum {
+    QCOW2_FEAT_TYPE_INCOMPATIBLE    = 0,
+    QCOW2_FEAT_TYPE_COMPATIBLE      = 1,
+    QCOW2_FEAT_TYPE_AUTOCLEAR       = 2,
+};
+
+typedef struct Qcow2Feature {
+    uint8_t type;
+    uint8_t bit;
+    char    name[46];
+} QEMU_PACKED Qcow2Feature;
+
 typedef struct BDRVQcowState {
     int cluster_bits;
     int cluster_size;
@@ -134,6 +156,14 @@ typedef struct BDRVQcowState {
     QCowSnapshot *snapshots;
 
     int flags;
+    int qcow_version;
+
+    uint64_t incompatible_features;
+    uint64_t compatible_features;
+    uint64_t autoclear_features;
+
+    size_t unknown_header_fields_size;
+    void* unknown_header_fields;
     QLIST_HEAD(, Qcow2UnknownHeaderExtension) unknown_header_ext;
 } BDRVQcowState;
 
@@ -164,6 +194,19 @@ typedef struct QCowL2Meta
     QLIST_ENTRY(QCowL2Meta) next_in_flight;
 } QCowL2Meta;
 
+enum {
+    QCOW2_CLUSTER_UNALLOCATED,
+    QCOW2_CLUSTER_NORMAL,
+    QCOW2_CLUSTER_COMPRESSED,
+    QCOW2_CLUSTER_ZERO
+};
+
+#define L1E_OFFSET_MASK 0x00ffffffffffff00ULL
+#define L2E_OFFSET_MASK 0x00ffffffffffff00ULL
+#define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffffffffffffffULL
+
+#define REFT_OFFSET_MASK 0xffffffffffffff00ULL
+
 static inline int size_to_clusters(BDRVQcowState *s, int64_t size)
 {
     return (size + (s->cluster_size - 1)) >> s->cluster_bits;
@@ -181,6 +224,19 @@ static inline int64_t align_offset(int64_t offset, int n)
     return offset;
 }
 
+static inline int qcow2_get_cluster_type(uint64_t l2_entry)
+{
+    if (l2_entry & QCOW_OFLAG_COMPRESSED) {
+        return QCOW2_CLUSTER_COMPRESSED;
+    } else if (l2_entry & QCOW_OFLAG_ZERO) {
+        return QCOW2_CLUSTER_ZERO;
+    } else if (!(l2_entry & L2E_OFFSET_MASK)) {
+        return QCOW2_CLUSTER_UNALLOCATED;
+    } else {
+        return QCOW2_CLUSTER_NORMAL;
+    }
+}
+
 
 // FIXME Need qcow2_ prefix to global functions
 
@@ -227,6 +283,7 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m);
 int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
     int nb_sectors);
+int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);
 
 /* qcow2-snapshot.c functions */
 int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
diff --git a/block/rbd.c b/block/rbd.c
index 46a8579..6cd8448 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -504,7 +504,7 @@ static int qemu_rbd_open(BlockDriverState *bs, const char *filename, int flags)
     fcntl(s->fds[0], F_SETFL, O_NONBLOCK);
     fcntl(s->fds[1], F_SETFL, O_NONBLOCK);
     qemu_aio_set_fd_handler(s->fds[RBD_FD_READ], qemu_rbd_aio_event_reader,
-                            NULL, qemu_rbd_aio_flush_cb, NULL, s);
+                            NULL, qemu_rbd_aio_flush_cb, s);
 
 
     return 0;
@@ -525,8 +525,7 @@ static void qemu_rbd_close(BlockDriverState *bs)
 
     close(s->fds[0]);
     close(s->fds[1]);
-    qemu_aio_set_fd_handler(s->fds[RBD_FD_READ], NULL , NULL, NULL, NULL,
-        NULL);
+    qemu_aio_set_fd_handler(s->fds[RBD_FD_READ], NULL, NULL, NULL, NULL);
 
     rbd_close(s->image);
     rados_ioctx_destroy(s->io_ctx);
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 3eaf625..0ed6b19 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -799,8 +799,7 @@ static int get_sheep_fd(BDRVSheepdogState *s)
         return -1;
     }
 
-    qemu_aio_set_fd_handler(fd, co_read_response, NULL, aio_flush_request,
-                            NULL, s);
+    qemu_aio_set_fd_handler(fd, co_read_response, NULL, aio_flush_request, s);
     return fd;
 }
 
@@ -973,7 +972,7 @@ static int coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
     qemu_co_mutex_lock(&s->lock);
     s->co_send = qemu_coroutine_self();
     qemu_aio_set_fd_handler(s->fd, co_read_response, co_write_request,
-                            aio_flush_request, NULL, s);
+                            aio_flush_request, s);
     socket_set_cork(s->fd, 1);
 
     /* send a header */
@@ -995,7 +994,7 @@ static int coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
 
     socket_set_cork(s->fd, 0);
     qemu_aio_set_fd_handler(s->fd, co_read_response, NULL,
-                            aio_flush_request, NULL, s);
+                            aio_flush_request, s);
     qemu_co_mutex_unlock(&s->lock);
 
     return 0;
@@ -1135,7 +1134,7 @@ static int sd_open(BlockDriverState *bs, const char *filename, int flags)
     g_free(buf);
     return 0;
 out:
-    qemu_aio_set_fd_handler(s->fd, NULL, NULL, NULL, NULL, NULL);
+    qemu_aio_set_fd_handler(s->fd, NULL, NULL, NULL, NULL);
     if (s->fd >= 0) {
         closesocket(s->fd);
     }
@@ -1349,7 +1348,7 @@ static void sd_close(BlockDriverState *bs)
         error_report("%s, %s", sd_strerror(rsp->result), s->name);
     }
 
-    qemu_aio_set_fd_handler(s->fd, NULL, NULL, NULL, NULL, NULL);
+    qemu_aio_set_fd_handler(s->fd, NULL, NULL, NULL, NULL);
     closesocket(s->fd);
     if (s->cache_enabled) {
         closesocket(s->flush_fd);
diff --git a/block_int.h b/block_int.h
index 0e5a032..0acb49f 100644
--- a/block_int.h
+++ b/block_int.h
@@ -50,6 +50,7 @@
 #define BLOCK_OPT_TABLE_SIZE    "table_size"
 #define BLOCK_OPT_PREALLOC      "preallocation"
 #define BLOCK_OPT_SUBFMT        "subformat"
+#define BLOCK_OPT_COMPAT_LEVEL  "compat"
 
 typedef struct BdrvTrackedRequest BdrvTrackedRequest;
 
diff --git a/cmd.c b/cmd.c
index 0806e18..7ffbb71 100644
--- a/cmd.c
+++ b/cmd.c
@@ -25,6 +25,7 @@
 
 #include "cmd.h"
 #include "qemu-aio.h"
+#include "main-loop.h"
 
 #define _(x)	x	/* not gettext support yet */
 
@@ -146,7 +147,7 @@ static void prep_fetchline(void *opaque)
 {
     int *fetchable = opaque;
 
-    qemu_aio_set_fd_handler(STDIN_FILENO, NULL, NULL, NULL, NULL, NULL);
+    qemu_set_fd_handler(STDIN_FILENO, NULL, NULL, NULL);
     *fetchable= 1;
 }
 
@@ -193,12 +194,11 @@ void command_loop(void)
         if (!prompted) {
             printf("%s", get_prompt());
             fflush(stdout);
-            qemu_aio_set_fd_handler(STDIN_FILENO, prep_fetchline, NULL, NULL,
-                                    NULL, &fetchable);
+            qemu_set_fd_handler(STDIN_FILENO, prep_fetchline, NULL, &fetchable);
             prompted = 1;
         }
 
-        qemu_aio_wait();
+        main_loop_wait(false);
 
         if (!fetchable) {
             continue;
@@ -221,7 +221,7 @@ void command_loop(void)
         prompted = 0;
         fetchable = 0;
     }
-    qemu_aio_set_fd_handler(STDIN_FILENO, NULL, NULL, NULL, NULL, NULL);
+    qemu_set_fd_handler(STDIN_FILENO, NULL, NULL, NULL);
 }
 
 /* from libxcmd/input.c */
diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt
index b6adcad..65e6325 100644
--- a/docs/specs/qcow2.txt
+++ b/docs/specs/qcow2.txt
@@ -18,7 +18,7 @@ The first cluster of a qcow2 image contains the file header:
                     QCOW magic string ("QFI\xfb")
 
           4 -  7:   version
-                    Version number (only valid value is 2)
+                    Version number (valid values are 2 and 3)
 
           8 - 15:   backing_file_offset
                     Offset into the image file at which the backing file name
@@ -67,12 +67,45 @@ The first cluster of a qcow2 image contains the file header:
                     Offset into the image file at which the snapshot table
                     starts. Must be aligned to a cluster boundary.
 
+If the version is 3 or higher, the header has the following additional fields.
+For version 2, the values are assumed to be zero, unless specified otherwise
+in the description of a field.
+
+         72 -  79:  incompatible_features
+                    Bitmask of incompatible features. An implementation must
+                    fail to open an image if an unknown bit is set.
+
+                    Bits 0-63:  Reserved (set to 0)
+
+         80 -  87:  compatible_features
+                    Bitmask of compatible features. An implementation can
+                    safely ignore any unknown bits that are set.
+
+                    Bits 0-63:  Reserved (set to 0)
+
+         88 -  95:  autoclear_features
+                    Bitmask of auto-clear features. An implementation may only
+                    write to an image with unknown auto-clear features if it
+                    clears the respective bits from this field first.
+
+                    Bits 0-63:  Reserved (set to 0)
+
+         96 -  99:  refcount_order
+                    Describes the width of a reference count block entry (width
+                    in bits = 1 << refcount_order). For version 2 images, the
+                    order is always assumed to be 4 (i.e. the width is 16 bits).
+
+        100 - 103:  header_length
+                    Length of the header structure in bytes. For version 2
+                    images, the length is always assumed to be 72 bytes.
+
 Directly after the image header, optional sections called header extensions can
 be stored. Each extension has a structure like the following:
 
     Byte  0 -  3:   Header extension type:
                         0x00000000 - End of the header extension area
                         0xE2792ACA - Backing file format name
+                        0x6803f857 - Feature name table
                         other      - Unknown header extension, can be safely
                                      ignored
 
@@ -83,9 +116,37 @@ be stored. Each extension has a structure like the following:
           n -  m:   Padding to round up the header extension size to the next
                     multiple of 8.
 
+Unless stated otherwise, each header extension type shall appear at most once
+in the same image.
+
 The remaining space between the end of the header extension area and the end of
-the first cluster can be used for other data. Usually, the backing file name is
-stored there.
+the first cluster can be used for the backing file name. It is not allowed to
+store other data here, so that an implementation can safely modify the header
+and add extensions without harming data of compatible features that it
+doesn't support. Compatible features that need space for additional data can
+use a header extension.
+
+
+== Feature name table ==
+
+The feature name table is an optional header extension that contains the name
+for features used by the image. It can be used by applications that don't know
+the respective feature (e.g. because the feature was introduced only later) to
+display a useful error message.
+
+The number of entries in the feature name table is determined by the length of
+the header extension data. Each entry look like this:
+
+    Byte       0:   Type of feature (select feature bitmap)
+                        0: Incompatible feature
+                        1: Compatible feature
+                        2: Autoclear feature
+
+               1:   Bit number within the selected feature bitmap (valid
+                    values: 0-63)
+
+          2 - 47:   Feature name (padded with zeros, but not necessarily null
+                    terminated if it has full length)
 
 
 == Host cluster management ==
@@ -126,9 +187,11 @@ Refcount table entry:
                     been allocated. All refcounts managed by this refcount block
                     are 0.
 
-Refcount block entry:
+Refcount block entry (x = refcount_bits - 1):
 
-    Bit  0 - 15:    Reference count of the cluster
+    Bit  0 -  x:    Reference count of the cluster. If refcount_bits implies a
+                    sub-byte width, note that bit 0 means the least significant
+                    bit in this context.
 
 
 == Cluster mapping ==
@@ -168,9 +231,29 @@ L1 table entry:
                     refcount is exactly one. This information is only accurate
                     in the active L1 table.
 
-L2 table entry (for normal clusters):
+L2 table entry:
 
-    Bit  0 -  8:    Reserved (set to 0)
+    Bit  0 -  61:   Cluster descriptor
+
+              62:   0 for standard clusters
+                    1 for compressed clusters
+
+              63:   0 for a cluster that is unused or requires COW, 1 if its
+                    refcount is exactly one. This information is only accurate
+                    in L2 tables that are reachable from the the active L1
+                    table.
+
+Standard Cluster Descriptor:
+
+    Bit       0:    If set to 1, the cluster reads as all zeros. The host
+                    cluster offset can be used to describe a preallocation,
+                    but it won't be used for reading data from this cluster,
+                    nor is data read from the backing file if the cluster is
+                    unallocated.
+
+                    With version 2, this is always 0.
+
+         1 -  8:    Reserved (set to 0)
 
          9 - 55:    Bits 9-55 of host cluster offset. Must be aligned to a
                     cluster boundary. If the offset is 0, the cluster is
@@ -178,30 +261,18 @@ L2 table entry (for normal clusters):
 
         56 - 61:    Reserved (set to 0)
 
-             62:    0 (this cluster is not compressed)
 
-             63:    0 for a cluster that is unused or requires COW, 1 if its
-                    refcount is exactly one. This information is only accurate
-                    in L2 tables that are reachable from the the active L1
-                    table.
-
-L2 table entry (for compressed clusters; x = 62 - (cluster_size - 8)):
+Compressed Clusters Descriptor (x = 62 - (cluster_size - 8)):
 
     Bit  0 -  x:    Host cluster offset. This is usually _not_ aligned to a
                     cluster boundary!
 
        x+1 - 61:    Compressed size of the images in sectors of 512 bytes
 
-             62:    1 (this cluster is compressed using zlib)
-
-             63:    0 for a cluster that is unused or requires COW, 1 if its
-                    refcount is exactly one. This information is only accurate
-                    in L2 tables that are reachable from the the active L1
-                    table.
-
 If a cluster is unallocated, read requests shall read the data from the backing
-file. If there is no backing file or the backing file is smaller than the image,
-they shall read zeros for all parts that are not covered by the backing file.
+file (except if bit 0 in the Standard Cluster Descriptor is set). If there is
+no backing file or the backing file is smaller than the image, they shall read
+zeros for all parts that are not covered by the backing file.
 
 
 == Snapshots ==
@@ -261,6 +332,11 @@ Snapshot table entry:
                                     state is saved. If this field is present,
                                     the 32-bit value in bytes 32-35 is ignored.
 
+                    Byte 48 - 55:   Virtual disk size of the snapshot in bytes
+
+                    Version 3 images must include extra data at least up to
+                    byte 55.
+
         variable:   Unique ID string for the snapshot (not null terminated)
 
         variable:   Name of the snapshot (not null terminated)
diff --git a/hw/ide/core.c b/hw/ide/core.c
index 35723fd..a5216a6 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -471,40 +471,68 @@ static void ide_rw_error(IDEState *s) {
     ide_set_irq(s->bus);
 }
 
+static void ide_sector_read_cb(void *opaque, int ret)
+{
+    IDEState *s = opaque;
+    int n;
+
+    s->pio_aiocb = NULL;
+    s->status &= ~BUSY_STAT;
+
+    bdrv_acct_done(s->bs, &s->acct);
+    if (ret != 0) {
+        if (ide_handle_rw_error(s, -ret, BM_STATUS_PIO_RETRY |
+                                BM_STATUS_RETRY_READ)) {
+            return;
+        }
+    }
+
+    n = s->nsector;
+    if (n > s->req_nb_sectors) {
+        n = s->req_nb_sectors;
+    }
+
+    /* Allow the guest to read the io_buffer */
+    ide_transfer_start(s, s->io_buffer, n * BDRV_SECTOR_SIZE, ide_sector_read);
+
+    ide_set_irq(s->bus);
+
+    ide_set_sector(s, ide_get_sector(s) + n);
+    s->nsector -= n;
+}
+
 void ide_sector_read(IDEState *s)
 {
     int64_t sector_num;
-    int ret, n;
+    int n;
 
     s->status = READY_STAT | SEEK_STAT;
     s->error = 0; /* not needed by IDE spec, but needed by Windows */
     sector_num = ide_get_sector(s);
     n = s->nsector;
+
     if (n == 0) {
-        /* no more sector to read from disk */
         ide_transfer_stop(s);
-    } else {
+        return;
+    }
+
+    s->status |= BUSY_STAT;
+
+    if (n > s->req_nb_sectors) {
+        n = s->req_nb_sectors;
+    }
+
 #if defined(DEBUG_IDE)
-        printf("read sector=%" PRId64 "\n", sector_num);
+    printf("sector=%" PRId64 "\n", sector_num);
 #endif
-        if (n > s->req_nb_sectors)
-            n = s->req_nb_sectors;
 
-        bdrv_acct_start(s->bs, &s->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
-        ret = bdrv_read(s->bs, sector_num, s->io_buffer, n);
-        bdrv_acct_done(s->bs, &s->acct);
-        if (ret != 0) {
-            if (ide_handle_rw_error(s, -ret,
-                BM_STATUS_PIO_RETRY | BM_STATUS_RETRY_READ))
-            {
-                return;
-            }
-        }
-        ide_transfer_start(s, s->io_buffer, 512 * n, ide_sector_read);
-        ide_set_irq(s->bus);
-        ide_set_sector(s, sector_num + n);
-        s->nsector -= n;
-    }
+    s->iov.iov_base = s->io_buffer;
+    s->iov.iov_len  = n * BDRV_SECTOR_SIZE;
+    qemu_iovec_init_external(&s->qiov, &s->iov, 1);
+
+    bdrv_acct_start(s->bs, &s->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
+    s->pio_aiocb = bdrv_aio_readv(s->bs, sector_num, &s->qiov, n,
+                                  ide_sector_read_cb, s);
 }
 
 static void dma_buf_commit(IDEState *s)
@@ -660,40 +688,39 @@ static void ide_sector_write_timer_cb(void *opaque)
     ide_set_irq(s->bus);
 }
 
-void ide_sector_write(IDEState *s)
+static void ide_sector_write_cb(void *opaque, int ret)
 {
-    int64_t sector_num;
-    int ret, n, n1;
-
-    s->status = READY_STAT | SEEK_STAT;
-    sector_num = ide_get_sector(s);
-#if defined(DEBUG_IDE)
-    printf("write sector=%" PRId64 "\n", sector_num);
-#endif
-    n = s->nsector;
-    if (n > s->req_nb_sectors)
-        n = s->req_nb_sectors;
+    IDEState *s = opaque;
+    int n;
 
-    bdrv_acct_start(s->bs, &s->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
-    ret = bdrv_write(s->bs, sector_num, s->io_buffer, n);
     bdrv_acct_done(s->bs, &s->acct);
 
+    s->pio_aiocb = NULL;
+    s->status &= ~BUSY_STAT;
+
     if (ret != 0) {
-        if (ide_handle_rw_error(s, -ret, BM_STATUS_PIO_RETRY))
+        if (ide_handle_rw_error(s, -ret, BM_STATUS_PIO_RETRY)) {
             return;
+        }
     }
 
+    n = s->nsector;
+    if (n > s->req_nb_sectors) {
+        n = s->req_nb_sectors;
+    }
     s->nsector -= n;
     if (s->nsector == 0) {
         /* no more sectors to write */
         ide_transfer_stop(s);
     } else {
-        n1 = s->nsector;
-        if (n1 > s->req_nb_sectors)
+        int n1 = s->nsector;
+        if (n1 > s->req_nb_sectors) {
             n1 = s->req_nb_sectors;
-        ide_transfer_start(s, s->io_buffer, 512 * n1, ide_sector_write);
+        }
+        ide_transfer_start(s, s->io_buffer, n1 * BDRV_SECTOR_SIZE,
+                           ide_sector_write);
     }
-    ide_set_sector(s, sector_num + n);
+    ide_set_sector(s, ide_get_sector(s) + n);
 
     if (win2k_install_hack && ((++s->irq_count % 16) == 0)) {
         /* It seems there is a bug in the Windows 2000 installer HDD
@@ -709,6 +736,30 @@ void ide_sector_write(IDEState *s)
     }
 }
 
+void ide_sector_write(IDEState *s)
+{
+    int64_t sector_num;
+    int n;
+
+    s->status = READY_STAT | SEEK_STAT | BUSY_STAT;
+    sector_num = ide_get_sector(s);
+#if defined(DEBUG_IDE)
+    printf("sector=%" PRId64 "\n", sector_num);
+#endif
+    n = s->nsector;
+    if (n > s->req_nb_sectors) {
+        n = s->req_nb_sectors;
+    }
+
+    s->iov.iov_base = s->io_buffer;
+    s->iov.iov_len  = n * BDRV_SECTOR_SIZE;
+    qemu_iovec_init_external(&s->qiov, &s->iov, 1);
+
+    bdrv_acct_start(s->bs, &s->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
+    s->pio_aiocb = bdrv_aio_writev(s->bs, sector_num, &s->qiov, n,
+                                   ide_sector_write_cb, s);
+}
+
 static void ide_flush_cb(void *opaque, int ret)
 {
     IDEState *s = opaque;
@@ -1765,6 +1816,12 @@ static void ide_reset(IDEState *s)
 #ifdef DEBUG_IDE
     printf("ide: reset\n");
 #endif
+
+    if (s->pio_aiocb) {
+        bdrv_aio_cancel(s->pio_aiocb);
+        s->pio_aiocb = NULL;
+    }
+
     if (s->drive_kind == IDE_CFATA)
         s->mult_sectors = 0;
     else
diff --git a/hw/ide/internal.h b/hw/ide/internal.h
index 100efd3..f8a027d 100644
--- a/hw/ide/internal.h
+++ b/hw/ide/internal.h
@@ -385,6 +385,9 @@ struct IDEState {
     int cd_sector_size;
     int atapi_dma; /* true if dma is requested for the packet cmd */
     BlockAcctCookie acct;
+    BlockDriverAIOCB *pio_aiocb;
+    struct iovec iov;
+    QEMUIOVector qiov;
     /* ATA DMA state */
     int io_buffer_size;
     QEMUSGList sg;
diff --git a/linux-aio.c b/linux-aio.c
index 15261ec..fa0fbf3 100644
--- a/linux-aio.c
+++ b/linux-aio.c
@@ -214,7 +214,7 @@ void *laio_init(void)
         goto out_close_efd;
 
     qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
-        qemu_laio_flush_cb, NULL, s);
+        qemu_laio_flush_cb, s);
 
     return s;
 
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index d311d13..68361f5 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -468,26 +468,37 @@ static int qemu_paio_error(struct qemu_paiocb *aiocb)
     return ret;
 }
 
-static int posix_aio_process_queue(void *opaque)
+static void posix_aio_read(void *opaque)
 {
     PosixAioState *s = opaque;
     struct qemu_paiocb *acb, **pacb;
     int ret;
-    int result = 0;
+    ssize_t len;
+
+    /* read all bytes from signal pipe */
+    for (;;) {
+        char bytes[16];
+
+        len = read(s->rfd, bytes, sizeof(bytes));
+        if (len == -1 && errno == EINTR)
+            continue; /* try again */
+        if (len == sizeof(bytes))
+            continue; /* more to read */
+        break;
+    }
 
     for(;;) {
         pacb = &s->first_aio;
         for(;;) {
             acb = *pacb;
             if (!acb)
-                return result;
+                return;
 
             ret = qemu_paio_error(acb);
             if (ret == ECANCELED) {
                 /* remove the request */
                 *pacb = acb->next;
                 qemu_aio_release(acb);
-                result = 1;
             } else if (ret != EINPROGRESS) {
                 /* end of aio */
                 if (ret == 0) {
@@ -507,35 +518,12 @@ static int posix_aio_process_queue(void *opaque)
                 /* call the callback */
                 acb->common.cb(acb->common.opaque, ret);
                 qemu_aio_release(acb);
-                result = 1;
                 break;
             } else {
                 pacb = &acb->next;
             }
         }
     }
-
-    return result;
-}
-
-static void posix_aio_read(void *opaque)
-{
-    PosixAioState *s = opaque;
-    ssize_t len;
-
-    /* read all bytes from signal pipe */
-    for (;;) {
-        char bytes[16];
-
-        len = read(s->rfd, bytes, sizeof(bytes));
-        if (len == -1 && errno == EINTR)
-            continue; /* try again */
-        if (len == sizeof(bytes))
-            continue; /* more to read */
-        break;
-    }
-
-    posix_aio_process_queue(s);
 }
 
 static int posix_aio_flush(void *opaque)
@@ -675,8 +663,7 @@ int paio_init(void)
     fcntl(s->rfd, F_SETFL, O_NONBLOCK);
     fcntl(s->wfd, F_SETFL, O_NONBLOCK);
 
-    qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
-        posix_aio_process_queue, s);
+    qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush, s);
 
     ret = pthread_attr_init(&attr);
     if (ret)
diff --git a/qemu-aio.h b/qemu-aio.h
index 230c2f7..bfdd35f 100644
--- a/qemu-aio.h
+++ b/qemu-aio.h
@@ -41,11 +41,6 @@ void qemu_aio_release(void *p);
 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
 typedef int (AioFlushHandler)(void *opaque);
 
-/* Runs all currently allowed AIO callbacks of completed requests in the
- * respective AIO backend. Returns 0 if no requests was handled, non-zero
- * if at least one queued request was handled. */
-typedef int (AioProcessQueue)(void *opaque);
-
 /* Flush any pending AIO operation. This function will block until all
  * outstanding AIO operations have been completed or cancelled. */
 void qemu_aio_flush(void);
@@ -53,15 +48,10 @@ void qemu_aio_flush(void);
 /* Wait for a single AIO completion to occur.  This function will wait
  * until a single AIO event has completed and it will ensure something
  * has moved before returning. This can issue new pending aio as
- * result of executing I/O completion or bh callbacks. */
-void qemu_aio_wait(void);
-
-/*
- * Runs all currently allowed AIO callbacks of completed requests. Returns 0
- * if no requests were handled, non-zero if at least one request was
- * processed.
- */
-int qemu_aio_process_queue(void);
+ * result of executing I/O completion or bh callbacks.
+ *
+ * Return whether there is still any pending AIO operation.  */
+bool qemu_aio_wait(void);
 
 /* Register a file descriptor and associated callbacks.  Behaves very similarly
  * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
@@ -74,7 +64,6 @@ int qemu_aio_set_fd_handler(int fd,
                             IOHandler *io_read,
                             IOHandler *io_write,
                             AioFlushHandler *io_flush,
-                            AioProcessQueue *io_process_queue,
                             void *opaque);
 
 #endif
diff --git a/qemu-coroutine-sleep.c b/qemu-coroutine-sleep.c
index fd65274..d7083ee 100644
--- a/qemu-coroutine-sleep.c
+++ b/qemu-coroutine-sleep.c
@@ -23,7 +23,6 @@ static void co_sleep_cb(void *opaque)
 {
     CoSleepCB *sleep_cb = opaque;
 
-    qemu_free_timer(sleep_cb->ts);
     qemu_coroutine_enter(sleep_cb->co, NULL);
 }
 
@@ -35,4 +34,6 @@ void coroutine_fn co_sleep_ns(QEMUClock *clock, int64_t ns)
     sleep_cb.ts = qemu_new_timer(clock, SCALE_NS, co_sleep_cb, &sleep_cb);
     qemu_mod_timer(sleep_cb.ts, qemu_get_clock_ns(clock) + ns);
     qemu_coroutine_yield();
+    qemu_del_timer(sleep_cb.ts);
+    qemu_free_timer(sleep_cb.ts);
 }
diff --git a/qemu-img.c b/qemu-img.c
index 6a61ca8..0ae543c 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -66,8 +66,8 @@ static void help(void)
            "  'filename' is a disk image filename\n"
            "  'fmt' is the disk image format. It is guessed automatically in most cases\n"
            "  'cache' is the cache mode used to write the output disk image, the valid\n"
-           "    options are: 'none', 'writeback' (default), 'writethrough', 'directsync'\n"
-           "    and 'unsafe'\n"
+           "    options are: 'none', 'writeback' (default, except for convert), 'writethrough',\n"
+           "    'directsync' and 'unsafe' (default for convert)\n"
            "  'size' is the disk image size in bytes. Optional suffixes\n"
            "    'k' or 'K' (kilobyte, 1024), 'M' (megabyte, 1024k), 'G' (gigabyte, 1024M)\n"
            "    and T (terabyte, 1024G) are supported. 'b' is ignored.\n"
diff --git a/qemu-io.c b/qemu-io.c
index e6fcd77..b48364f 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -15,6 +15,7 @@
 #include <libgen.h>
 
 #include "qemu-common.h"
+#include "main-loop.h"
 #include "block_int.h"
 #include "cmd.h"
 #include "trace/control.h"
@@ -295,7 +296,7 @@ static int do_aio_readv(QEMUIOVector *qiov, int64_t offset, int *total)
     bdrv_aio_readv(bs, offset >> 9, qiov, qiov->size >> 9,
                    aio_rw_done, &async_ret);
     while (async_ret == NOT_DONE) {
-        qemu_aio_wait();
+        main_loop_wait(false);
     }
 
     *total = qiov->size;
@@ -309,7 +310,7 @@ static int do_aio_writev(QEMUIOVector *qiov, int64_t offset, int *total)
     bdrv_aio_writev(bs, offset >> 9, qiov, qiov->size >> 9,
                     aio_rw_done, &async_ret);
     while (async_ret == NOT_DONE) {
-        qemu_aio_wait();
+        main_loop_wait(false);
     }
 
     *total = qiov->size;
@@ -352,7 +353,7 @@ static int do_aio_multiwrite(BlockRequest* reqs, int num_reqs, int *total)
     }
 
     while (async_ret.num_done < num_reqs) {
-        qemu_aio_wait();
+        main_loop_wait(false);
     }
 
     return async_ret.error < 0 ? async_ret.error : 1;
@@ -1784,6 +1785,7 @@ static void usage(const char *name)
 "  -g, --growable       allow file to grow (only applies to protocols)\n"
 "  -m, --misalign       misalign allocations for O_DIRECT\n"
 "  -k, --native-aio     use kernel AIO implementation (on Linux only)\n"
+"  -t, --cache=MODE     use the given cache mode for the image\n"
 "  -T, --trace FILE     enable trace events listed in the given file\n"
 "  -h, --help           display this help and exit\n"
 "  -V, --version        output version information and exit\n"
@@ -1796,7 +1798,7 @@ int main(int argc, char **argv)
 {
     int readonly = 0;
     int growable = 0;
-    const char *sopt = "hVc:rsnmgkT:";
+    const char *sopt = "hVc:rsnmgkt:T:";
     const struct option lopt[] = {
         { "help", 0, NULL, 'h' },
         { "version", 0, NULL, 'V' },
@@ -1808,6 +1810,7 @@ int main(int argc, char **argv)
         { "misalign", 0, NULL, 'm' },
         { "growable", 0, NULL, 'g' },
         { "native-aio", 0, NULL, 'k' },
+        { "cache", 1, NULL, 't' },
         { "trace", 1, NULL, 'T' },
         { NULL, 0, NULL, 0 }
     };
@@ -1840,6 +1843,12 @@ int main(int argc, char **argv)
         case 'k':
             flags |= BDRV_O_NATIVE_AIO;
             break;
+        case 't':
+            if (bdrv_parse_cache_flags(optarg, &flags) < 0) {
+                error_report("Invalid cache option: %s", optarg);
+                exit(1);
+            }
+            break;
         case 'T':
             if (!trace_backend_init(optarg, NULL)) {
                 exit(1); /* error message will have been printed */
diff --git a/qemu-tool.c b/qemu-tool.c
index edb84f5..6579b00 100644
--- a/qemu-tool.c
+++ b/qemu-tool.c
@@ -61,7 +61,7 @@ void monitor_protocol_event(MonitorEvent event, QObject *data)
 
 int64_t cpu_get_clock(void)
 {
-    return 0;
+    return qemu_get_clock_ns(rt_clock);
 }
 
 int64_t cpu_get_icount(void)
@@ -87,7 +87,6 @@ int qemu_init_main_loop(void)
 {
     init_clocks();
     init_timer_alarm();
-    qemu_clock_enable(vm_clock, false);
     return main_loop_init();
 }
 
diff --git a/tests/qemu-iotests/005 b/tests/qemu-iotests/005
index 74537db..b7970e3 100755
--- a/tests/qemu-iotests/005
+++ b/tests/qemu-iotests/005
@@ -65,7 +65,7 @@ $QEMU_IO -c "read 1024 4096" $TEST_IMG | _filter_qemu_io
 
 echo
 echo "small write"
-$QEMU_IO -c "read 8192 4096" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write 8192 4096" $TEST_IMG | _filter_qemu_io
 
 # success, all done
 echo "*** done"
diff --git a/tests/qemu-iotests/005.out b/tests/qemu-iotests/005.out
index 718a185..2d3e7df 100644
--- a/tests/qemu-iotests/005.out
+++ b/tests/qemu-iotests/005.out
@@ -8,6 +8,6 @@ read 4096/4096 bytes at offset 1024
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 small write
-read 4096/4096 bytes at offset 8192
+wrote 4096/4096 bytes at offset 8192
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 *** done
diff --git a/tests/qemu-iotests/013.out b/tests/qemu-iotests/013.out
index 3073e3f..0d57187 100644
--- a/tests/qemu-iotests/013.out
+++ b/tests/qemu-iotests/013.out
@@ -1,5 +1,5 @@
 QA output created by 013
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 cluster_size=4096 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 
 Testing empty image
 
 At offset 0:
diff --git a/tests/qemu-iotests/014.out b/tests/qemu-iotests/014.out
index 8045613..0258d75 100644
--- a/tests/qemu-iotests/014.out
+++ b/tests/qemu-iotests/014.out
@@ -1,5 +1,5 @@
 QA output created by 014
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 cluster_size=4096 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 
 Testing empty image:
 test2: With offset 0
 === Clusters to be compressed [1]
diff --git a/tests/qemu-iotests/015.out b/tests/qemu-iotests/015.out
index 3ba723d..d4b961c 100644
--- a/tests/qemu-iotests/015.out
+++ b/tests/qemu-iotests/015.out
@@ -1,7 +1,7 @@
 QA output created by 015
 
 creating image
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=37748736 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=37748736 
 creating first snapshot
 wrote 37748736/37748736 bytes at offset 0
 36 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
diff --git a/tests/qemu-iotests/019.out b/tests/qemu-iotests/019.out
index 241d30c..b51224b 100644
--- a/tests/qemu-iotests/019.out
+++ b/tests/qemu-iotests/019.out
@@ -1,5 +1,5 @@
 QA output created by 019
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 
 Filling base image
 
 === IO: pattern 42
@@ -269,7 +269,7 @@ qemu-io> wrote 65536/65536 bytes at offset 4296015872
 qemu-io> No errors were found on the image.
 Creating test image with backing file
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file='TEST_DIR/t.IMGFMT.base' cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file='TEST_DIR/t.IMGFMT.base' 
 Filling test image
 
 === IO: pattern 43
diff --git a/tests/qemu-iotests/022.out b/tests/qemu-iotests/022.out
index b900c71..aed86d5 100644
--- a/tests/qemu-iotests/022.out
+++ b/tests/qemu-iotests/022.out
@@ -1,5 +1,5 @@
 QA output created by 022
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 cluster_size=4096 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 
 Testing empty image
 
 At offset 10485760:
diff --git a/tests/qemu-iotests/023.out b/tests/qemu-iotests/023.out
index 138434e..8a7c5b2 100644
--- a/tests/qemu-iotests/023.out
+++ b/tests/qemu-iotests/023.out
@@ -1,7 +1,7 @@
 QA output created by 023
 Creating new image; cluster size: 1024
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 Testing empty image
 
 At offset 0:
@@ -5664,7 +5664,7 @@ qemu-io> read 3072/3072 bytes at offset 4295491072
 qemu-io> No errors were found on the image.
 Creating another new image
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 More complex patterns
 
 test2: With offset 0
@@ -5887,7 +5887,7 @@ qemu-io> read 2048/2048 bytes at offset 4295001088
 qemu-io> No errors were found on the image.
 Creating new image; cluster size: 4096
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=4096 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 Testing empty image
 
 At offset 0:
@@ -12270,7 +12270,7 @@ qemu-io> read 12288/12288 bytes at offset 4301256704
 qemu-io> No errors were found on the image.
 Creating another new image
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=4096 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 More complex patterns
 
 test2: With offset 0
@@ -12493,7 +12493,7 @@ qemu-io> read 8192/8192 bytes at offset 4295102464
 qemu-io> No errors were found on the image.
 Creating new image; cluster size: 16384
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=16384 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 Testing empty image
 
 At offset 0:
@@ -18876,7 +18876,7 @@ qemu-io> read 49152/49152 bytes at offset 4395622400
 qemu-io> No errors were found on the image.
 Creating another new image
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=16384 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 More complex patterns
 
 test2: With offset 0
@@ -19099,7 +19099,7 @@ qemu-io> read 32768/32768 bytes at offset 4295507968
 qemu-io> No errors were found on the image.
 Creating new image; cluster size: 65536
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 Testing empty image
 
 At offset 0:
@@ -25482,7 +25482,7 @@ qemu-io> read 196608/196608 bytes at offset 5905547264
 qemu-io> No errors were found on the image.
 Creating another new image
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=8589934592 
 More complex patterns
 
 test2: With offset 0
diff --git a/tests/qemu-iotests/024.out b/tests/qemu-iotests/024.out
index 4cee216..072207c 100644
--- a/tests/qemu-iotests/024.out
+++ b/tests/qemu-iotests/024.out
@@ -1,7 +1,7 @@
 QA output created by 024
 Creating backing file
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 === IO: pattern 0x11
 qemu-io> wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -21,7 +21,7 @@ qemu-io> wrote 65536/65536 bytes at offset 917504
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-io> Creating new backing file
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 === IO: pattern 0x22
 qemu-io> wrote 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -33,7 +33,7 @@ qemu-io> wrote 131072/131072 bytes at offset 786432
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-io> Creating COW image
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file='TEST_DIR/t.IMGFMT.base_old' cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file='TEST_DIR/t.IMGFMT.base_old' 
 === IO: pattern 0x33
 qemu-io> wrote 262144/262144 bytes at offset 0
 256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
diff --git a/tests/qemu-iotests/026.out b/tests/qemu-iotests/026.out
index b503cf2..fb4f20e 100644
--- a/tests/qemu-iotests/026.out
+++ b/tests/qemu-iotests/026.out
@@ -1,63 +1,63 @@
 QA output created by 026
 Errors while writing 128 kB
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_update; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 5; imm: off; once: on; write 
 wrote 131072/131072 bytes at offset 0
@@ -65,7 +65,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: Input/output error
 read failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 5; imm: off; once: on; write -b
 wrote 131072/131072 bytes at offset 0
@@ -73,7 +73,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: Input/output error
 read failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 5; imm: off; once: off; write 
 wrote 131072/131072 bytes at offset 0
@@ -81,7 +81,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: Input/output error
 read failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 5; imm: off; once: off; write -b
 wrote 131072/131072 bytes at offset 0
@@ -89,7 +89,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: Input/output error
 read failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 28; imm: off; once: on; write 
 wrote 131072/131072 bytes at offset 0
@@ -97,7 +97,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: No space left on device
 read failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 28; imm: off; once: on; write -b
 wrote 131072/131072 bytes at offset 0
@@ -105,7 +105,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: No space left on device
 read failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 28; imm: off; once: off; write 
 wrote 131072/131072 bytes at offset 0
@@ -113,7 +113,7 @@ wrote 131072/131072 bytes at offset 0
 write failed: No space left on device
 read failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_load; errno: 28; imm: off; once: off; write -b
 wrote 131072/131072 bytes at offset 0
@@ -121,306 +121,306 @@ wrote 131072/131072 bytes at offset 0
 write failed: No space left on device
 read failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_update; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 
 128 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l2_alloc.write; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 
 1 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: write_aio; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_load; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_update_part; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 5; imm: off; once: on; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 5; imm: off; once: on; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 5; imm: off; once: off; write 
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 5; imm: off; once: off; write -b
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: cluster_alloc; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
@@ -428,116 +428,116 @@ No errors were found on the image.
 
 === Refcout table growth tests ===
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.hookup; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.hookup; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.hookup; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
 55 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.hookup; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 
 251 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_blocks; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_blocks; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_blocks; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
 10 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_blocks; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 
 23 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_table; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_table; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_table; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
 10 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.write_table; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
 
 23 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.switch_table; errno: 28; imm: off; once: on; write 
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.switch_table; errno: 28; imm: off; once: on; write -b
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.switch_table; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
 10 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=512 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: refblock_alloc.switch_table; errno: 28; imm: off; once: off; write -b
 write failed: No space left on device
@@ -547,54 +547,54 @@ This means waste of disk space, but no harm to data.
 
 === L1 growth tests ===
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.alloc_table; errno: 5; imm: off; once: on
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.alloc_table; errno: 5; imm: off; once: off
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.alloc_table; errno: 28; imm: off; once: on
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.alloc_table; errno: 28; imm: off; once: off
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.write_table; errno: 5; imm: off; once: on
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.write_table; errno: 5; imm: off; once: off
 qcow2_free_clusters failed: Input/output error
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.write_table; errno: 28; imm: off; once: on
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.write_table; errno: 28; imm: off; once: off
 qcow2_free_clusters failed: No space left on device
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.activate_table; errno: 5; imm: off; once: on
 write failed: Input/output error
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.activate_table; errno: 5; imm: off; once: off
 qcow2_free_clusters failed: Input/output error
@@ -602,12 +602,12 @@ write failed: Input/output error
 
 96 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.activate_table; errno: 28; imm: off; once: on
 write failed: No space left on device
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
 Event: l1_grow.activate_table; errno: 28; imm: off; once: off
 qcow2_free_clusters failed: No space left on device
diff --git a/tests/qemu-iotests/029.out b/tests/qemu-iotests/029.out
index c2ad30c..0eedb3a 100644
--- a/tests/qemu-iotests/029.out
+++ b/tests/qemu-iotests/029.out
@@ -1,9 +1,9 @@
 QA output created by 029
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
 wrote 4096/4096 bytes at offset 0
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 No errors were found on the image.
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216 cluster_size=1024 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216 
 wrote 4194304/4194304 bytes at offset 0
 4 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 No errors were found on the image.
diff --git a/tests/qemu-iotests/031 b/tests/qemu-iotests/031
index 6365f28..2d5e3b1 100755
--- a/tests/qemu-iotests/031
+++ b/tests/qemu-iotests/031
@@ -45,26 +45,34 @@ _supported_proto generic
 _supported_os Linux
 
 CLUSTER_SIZE=65536
-echo
-echo === Create image with unknown header extension ===
-echo
-_make_test_img 64M
-./qcow2.py $TEST_IMG add-header-ext 0x12345678 "This is a test header extension"
-./qcow2.py $TEST_IMG dump-header
-_check_test_img
 
-echo
-echo === Rewrite header with no backing file ===
-echo
-$QEMU_IMG rebase -u -b "" $TEST_IMG
-./qcow2.py $TEST_IMG dump-header
-_check_test_img
+# qcow2.py output depends on the exact options used, so override the command
+# line here as an exception
+for IMGOPTS in "compat=0.10" "compat=1.1"; do
 
-echo
-echo === Add a backing file and format ===
-echo
-$QEMU_IMG rebase -u -b "/some/backing/file/path" -F host_device $TEST_IMG
-./qcow2.py $TEST_IMG dump-header
+    echo
+    echo ===== Testing with -o $IMGOPTS =====
+    echo
+    echo === Create image with unknown header extension ===
+    echo
+    _make_test_img 64M
+    ./qcow2.py $TEST_IMG add-header-ext 0x12345678 "This is a test header extension"
+    ./qcow2.py $TEST_IMG dump-header
+    _check_test_img
+
+    echo
+    echo === Rewrite header with no backing file ===
+    echo
+    $QEMU_IMG rebase -u -b "" $TEST_IMG
+    ./qcow2.py $TEST_IMG dump-header
+    _check_test_img
+
+    echo
+    echo === Add a backing file and format ===
+    echo
+    $QEMU_IMG rebase -u -b "/some/backing/file/path" -F host_device $TEST_IMG
+    ./qcow2.py $TEST_IMG dump-header
+done
 
 # success, all done
 echo "*** done"
diff --git a/tests/qemu-iotests/031.out b/tests/qemu-iotests/031.out
index 0f1bf68..d3cab30 100644
--- a/tests/qemu-iotests/031.out
+++ b/tests/qemu-iotests/031.out
@@ -1,8 +1,10 @@
 QA output created by 031
 
+===== Testing with -o compat=0.10 =====
+
 === Create image with unknown header extension ===
 
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 cluster_size=65536 
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
 magic                     0x514649fb
 version                   2
 backing_file_offset       0x0
@@ -16,6 +18,11 @@ refcount_table_offset     0x10000
 refcount_table_clusters   1
 nb_snapshots              0
 snapshot_offset           0x0
+incompatible_features     0x0
+compatible_features       0x0
+autoclear_features        0x0
+refcount_order            4
+header_length             72
 
 Header extension:
 magic                     0x12345678
@@ -39,6 +46,16 @@ refcount_table_offset     0x10000
 refcount_table_clusters   1
 nb_snapshots              0
 snapshot_offset           0x0
+incompatible_features     0x0
+compatible_features       0x0
+autoclear_features        0x0
+refcount_order            4
+header_length             72
+
+Header extension:
+magic                     0x6803f857
+length                    0
+data                      ''
 
 Header extension:
 magic                     0x12345678
@@ -51,7 +68,7 @@ No errors were found on the image.
 
 magic                     0x514649fb
 version                   2
-backing_file_offset       0x90
+backing_file_offset       0x98
 backing_file_size         0x17
 cluster_bits              16
 size                      67108864
@@ -62,6 +79,11 @@ refcount_table_offset     0x10000
 refcount_table_clusters   1
 nb_snapshots              0
 snapshot_offset           0x0
+incompatible_features     0x0
+compatible_features       0x0
+autoclear_features        0x0
+refcount_order            4
+header_length             72
 
 Header extension:
 magic                     0xe2792aca
@@ -69,6 +91,112 @@ length                    11
 data                      'host_device'
 
 Header extension:
+magic                     0x6803f857
+length                    0
+data                      ''
+
+Header extension:
+magic                     0x12345678
+length                    31
+data                      'This is a test header extension'
+
+
+===== Testing with -o compat=1.1 =====
+
+=== Create image with unknown header extension ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+magic                     0x514649fb
+version                   3
+backing_file_offset       0x0
+backing_file_size         0x0
+cluster_bits              16
+size                      67108864
+crypt_method              0
+l1_size                   1
+l1_table_offset           0x30000
+refcount_table_offset     0x10000
+refcount_table_clusters   1
+nb_snapshots              0
+snapshot_offset           0x0
+incompatible_features     0x0
+compatible_features       0x0
+autoclear_features        0x0
+refcount_order            4
+header_length             104
+
+Header extension:
+magic                     0x12345678
+length                    31
+data                      'This is a test header extension'
+
+No errors were found on the image.
+
+=== Rewrite header with no backing file ===
+
+magic                     0x514649fb
+version                   3
+backing_file_offset       0x0
+backing_file_size         0x0
+cluster_bits              16
+size                      67108864
+crypt_method              0
+l1_size                   1
+l1_table_offset           0x30000
+refcount_table_offset     0x10000
+refcount_table_clusters   1
+nb_snapshots              0
+snapshot_offset           0x0
+incompatible_features     0x0
+compatible_features       0x0
+autoclear_features        0x0
+refcount_order            4
+header_length             104
+
+Header extension:
+magic                     0x6803f857
+length                    0
+data                      ''
+
+Header extension:
+magic                     0x12345678
+length                    31
+data                      'This is a test header extension'
+
+No errors were found on the image.
+
+=== Add a backing file and format ===
+
+magic                     0x514649fb
+version                   3
+backing_file_offset       0xb8
+backing_file_size         0x17
+cluster_bits              16
+size                      67108864
+crypt_method              0
+l1_size                   1
+l1_table_offset           0x30000
+refcount_table_offset     0x10000
+refcount_table_clusters   1
+nb_snapshots              0
+snapshot_offset           0x0
+incompatible_features     0x0
+compatible_features       0x0
+autoclear_features        0x0
+refcount_order            4
+header_length             104
+
+Header extension:
+magic                     0xe2792aca
+length                    11
+data                      'host_device'
+
+Header extension:
+magic                     0x6803f857
+length                    0
+data                      ''
+
+Header extension:
 magic                     0x12345678
 length                    31
 data                      'This is a test header extension'
diff --git a/tests/qemu-iotests/032 b/tests/qemu-iotests/032
new file mode 100755
index 0000000..7155568
--- /dev/null
+++ b/tests/qemu-iotests/032
@@ -0,0 +1,69 @@
+#!/bin/bash
+#
+# Test that AIO requests are drained before an image is closed. This used
+# to segfault because the request coroutine kept running even after the
+# BlockDriverState was freed.
+#
+# Copyright (C) 2011 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+. ./common.pattern
+
+# This works for any image format (though unlikely to segfault for raw)
+_supported_fmt generic
+_supported_proto generic
+_supported_os Linux
+
+echo
+echo === Prepare image ===
+echo
+
+CLUSTER_SIZE=65536
+_make_test_img 64M
+
+# Allocate every other cluster so that afterwards a big write request will
+# actually loop a while and issue many I/O requests for the lower layer
+for i in $(seq 0 128 4096); do echo "write ${i}k 64k"; done | $QEMU_IO $TEST_IMG | _filter_qemu_io
+
+echo
+echo === AIO request during close ===
+echo
+$QEMU_IO -c "aio_write 0 4M" -c "close" $TEST_IMG | _filter_qemu_io
+_check_test_img
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/032.out b/tests/qemu-iotests/032.out
new file mode 100644
index 0000000..7272ac2
--- /dev/null
+++ b/tests/qemu-iotests/032.out
@@ -0,0 +1,78 @@
+QA output created by 032
+
+=== Prepare image ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+qemu-io> wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 131072
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 262144
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 393216
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 524288
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 655360
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 786432
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 917504
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1048576
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1179648
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1310720
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1441792
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1572864
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1703936
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1835008
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 1966080
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2097152
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2228224
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2359296
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2490368
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2621440
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2752512
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 2883584
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3014656
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3145728
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3276800
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3407872
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3538944
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3670016
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3801088
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 3932160
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 4063232
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> wrote 65536/65536 bytes at offset 4194304
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> 
+=== AIO request during close ===
+
+wrote 4194304/4194304 bytes at offset 0
+4 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+No errors were found on the image.
+*** done
diff --git a/tests/qemu-iotests/033 b/tests/qemu-iotests/033
new file mode 100755
index 0000000..9aee078
--- /dev/null
+++ b/tests/qemu-iotests/033
@@ -0,0 +1,73 @@
+#!/bin/bash
+#
+# Test aligned and misaligned write zeroes operations.
+#
+# Copyright (C) 2012 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=pbonzini@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt generic
+_supported_proto generic
+_supported_os Linux
+
+
+size=128M
+_make_test_img $size
+
+echo
+echo "== preparing image =="
+$QEMU_IO -c "write -P 0xa 0x200 0x400" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -P 0xa 0x20000 0x600" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -z 0x400 0x20000" $TEST_IMG | _filter_qemu_io
+
+echo
+echo "== verifying patterns (1) =="
+$QEMU_IO -c "read -P 0xa 0x200 0x200" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 0x400 0x20000" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xa 0x20400 0x200" $TEST_IMG | _filter_qemu_io
+
+echo
+echo "== rewriting zeroes =="
+$QEMU_IO -c "write -P 0xb 0x10000 0x10000" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -z 0x10000 0x10000" $TEST_IMG | _filter_qemu_io
+
+echo
+echo "== verifying patterns (2) =="
+$QEMU_IO -c "read -P 0x0 0x400 0x20000" $TEST_IMG | _filter_qemu_io
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/033.out b/tests/qemu-iotests/033.out
new file mode 100644
index 0000000..8934883
--- /dev/null
+++ b/tests/qemu-iotests/033.out
@@ -0,0 +1,29 @@
+QA output created by 033
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
+
+== preparing image ==
+wrote 1024/1024 bytes at offset 512
+1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 1536/1536 bytes at offset 131072
+2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 131072/131072 bytes at offset 1024
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verifying patterns (1) ==
+read 512/512 bytes at offset 512
+512.000000 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 131072/131072 bytes at offset 1024
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 512/512 bytes at offset 132096
+512.000000 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== rewriting zeroes ==
+wrote 65536/65536 bytes at offset 65536
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 65536
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verifying patterns (2) ==
+read 131072/131072 bytes at offset 1024
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+*** done
diff --git a/tests/qemu-iotests/034 b/tests/qemu-iotests/034
new file mode 100755
index 0000000..8254df8
--- /dev/null
+++ b/tests/qemu-iotests/034
@@ -0,0 +1,113 @@
+#!/bin/bash
+#
+# Test bdrv_write_zeroes with backing files
+#
+# Copyright (C) 2012 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow qcow2 vmdk qed
+_supported_proto generic
+_supported_os Linux
+
+CLUSTER_SIZE=4k
+size=128M
+
+echo
+echo "== creating backing file for COW tests =="
+
+_make_test_img $size
+$QEMU_IO -c "write -P 0x55 0 1M" $TEST_IMG | _filter_qemu_io
+mv $TEST_IMG $TEST_IMG.base
+
+_make_test_img -b $TEST_IMG.base 6G
+
+echo
+echo "== zero write with backing file =="
+$QEMU_IO -c "write -z 64k 192k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -z 513k 13k" $TEST_IMG | _filter_qemu_io
+
+_check_test_img
+
+echo
+echo "== verifying patterns (3) =="
+$QEMU_IO -c "read -P 0x55 0 64k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 64k 192k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x55 256k 257k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 513k 13k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x55 526k 498k" $TEST_IMG | _filter_qemu_io
+
+echo
+echo "== overwriting zero cluster =="
+$QEMU_IO -c "write -P 0xa 60k 8k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -P 0xb 64k 8k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -P 0xc 76k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -P 0xd 252k 8k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "write -P 0xe 248k 8k" $TEST_IMG | _filter_qemu_io
+
+_check_test_img
+
+echo
+echo "== verifying patterns (4) =="
+$QEMU_IO -c "read -P 0x55 0 60k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xa 60k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xb 64k 8k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 72k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xc 76k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 80k 168k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xe 248k 8k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xd 256k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x55 260k 64k" $TEST_IMG | _filter_qemu_io
+
+echo
+echo "== re-zeroing overwritten area =="
+$QEMU_IO -c "write -z 64k 192k" $TEST_IMG | _filter_qemu_io
+
+_check_test_img
+
+echo
+echo "== verifying patterns (5) =="
+$QEMU_IO -c "read -P 0x55 0 60k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xa 60k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 64k 192k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0xd 256k 4k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x55 260k 253k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x0 513k 13k" $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c "read -P 0x55 526k 498k" $TEST_IMG | _filter_qemu_io
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/034.out b/tests/qemu-iotests/034.out
new file mode 100644
index 0000000..e82dae5
--- /dev/null
+++ b/tests/qemu-iotests/034.out
@@ -0,0 +1,81 @@
+QA output created by 034
+
+== creating backing file for COW tests ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
+wrote 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file='TEST_DIR/t.IMGFMT.base' 
+
+== zero write with backing file ==
+wrote 196608/196608 bytes at offset 65536
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 13312/13312 bytes at offset 525312
+13 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+No errors were found on the image.
+
+== verifying patterns (3) ==
+read 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 196608/196608 bytes at offset 65536
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 263168/263168 bytes at offset 262144
+257 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 13312/13312 bytes at offset 525312
+13 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 509952/509952 bytes at offset 538624
+498 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== overwriting zero cluster ==
+wrote 8192/8192 bytes at offset 61440
+8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 8192/8192 bytes at offset 65536
+8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 4096/4096 bytes at offset 77824
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 8192/8192 bytes at offset 258048
+8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 8192/8192 bytes at offset 253952
+8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+No errors were found on the image.
+
+== verifying patterns (4) ==
+read 61440/61440 bytes at offset 0
+60 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 61440
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 8192/8192 bytes at offset 65536
+8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 73728
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 77824
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 172032/172032 bytes at offset 81920
+168 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 8192/8192 bytes at offset 253952
+8 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 262144
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65536/65536 bytes at offset 266240
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== re-zeroing overwritten area ==
+wrote 196608/196608 bytes at offset 65536
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+No errors were found on the image.
+
+== verifying patterns (5) ==
+read 61440/61440 bytes at offset 0
+60 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 61440
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 196608/196608 bytes at offset 65536
+192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 4096/4096 bytes at offset 262144
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 259072/259072 bytes at offset 266240
+253 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 13312/13312 bytes at offset 525312
+13 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 509952/509952 bytes at offset 538624
+498 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+*** done
diff --git a/tests/qemu-iotests/check b/tests/qemu-iotests/check
index aae1378..432732c 100755
--- a/tests/qemu-iotests/check
+++ b/tests/qemu-iotests/check
@@ -41,9 +41,6 @@ then
     exit 1
 fi
 
-# we need common
-. ./common
-
 # we need common.rc
 if ! . ./common.rc
 then
@@ -51,6 +48,9 @@ then
     exit 1
 fi
 
+# we need common
+. ./common
+
 #if [ `id -u` -ne 0 ]
 #then
 #    echo "check: QA must be run as root"
diff --git a/tests/qemu-iotests/common b/tests/qemu-iotests/common
index c187f6c..eeb70cb 100644
--- a/tests/qemu-iotests/common
+++ b/tests/qemu-iotests/common
@@ -35,6 +35,7 @@ diff="diff -u"
 verbose=false
 group=false
 xgroup=false
+imgopts=false
 showme=false
 sortme=false
 expunge=true
@@ -44,6 +45,7 @@ rm -f $tmp.list $tmp.tmp $tmp.sed
 
 export IMGFMT=raw
 export IMGPROTO=file
+export IMGOPTS=""
 export QEMU_IO_OPTIONS=""
 
 for r
@@ -103,6 +105,13 @@ s/ .*//p
 	mv $tmp.tmp $tmp.list
 	xgroup=false
 	continue
+
+    elif $imgopts
+    then
+        IMGOPTS="$r"
+        imgopts=false
+        continue
+
     fi
 
     xpand=true
@@ -130,6 +139,7 @@ check options
     -nocache		use O_DIRECT on backing file
     -misalign		misalign memory allocations
     -n			show me, do not run tests
+    -o options          -o options to pass to qemu-img create/convert
     -T			output timestamps
     -r 			randomize test order
     
@@ -223,6 +233,10 @@ testlist options
 	    showme=true
 	    xpand=false
 	    ;;
+        -o)
+            imgopts=true
+            xpand=false
+            ;;
         -r)	# randomize test order
 	    randomize=true
 	    xpand=false
@@ -299,6 +313,9 @@ BEGIN	{ for (t='$start'; t<='$end'; t++) printf "%03d\n",t }' \
 
 done
 
+# Set default options for qemu-img create -o if they were not specified
+_set_default_imgopts
+
 if [ -s $tmp.list ]
 then
     # found some valid test numbers ... this is good
diff --git a/tests/qemu-iotests/common.config b/tests/qemu-iotests/common.config
index a220684..df082e7 100644
--- a/tests/qemu-iotests/common.config
+++ b/tests/qemu-iotests/common.config
@@ -36,7 +36,7 @@ export LANG=C
 
 PATH=".:$PATH"
 
-HOST=`hostname -s`
+HOST=`hostname -s 2> /dev/null`
 HOSTOS=`uname -s`
 
 EMAIL=root@localhost    # where auto-qa will send its status messages
diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index 4cb8dae..4bc7420 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -53,21 +53,44 @@ else
     TEST_IMG=$IMGPROTO:$TEST_DIR/t.$IMGFMT
 fi
 
+_optstr_add()
+{
+    if [ -n "$1" ]; then
+        echo "$1,$2"
+    else
+        echo "$2"
+    fi
+}
+
+_set_default_imgopts()
+{
+    if [ "$IMGFMT" == "qcow2" ] && ! (echo "$IMGOPTS" | grep "compat=" > /dev/null); then
+        IMGOPTS=$(_optstr_add "$IMGOPTS" "compat=1.1")
+    fi
+}
+
 _make_test_img()
 {
     # extra qemu-img options can be added by tests
     # at least one argument (the image size) needs to be added
     local extra_img_options=""
-    local cluster_size_filter="s# cluster_size=[0-9]\\+##g"
     local image_size=$*
+    local optstr=""
+
+    if [ -n "$IMGOPTS" ]; then
+        optstr=$(_optstr_add "$optstr" "$IMGOPTS")
+    fi
 
     if [ "$1" = "-b" ]; then
         extra_img_options="$1 $2"
         image_size=$3
     fi
     if [ \( "$IMGFMT" = "qcow2" -o "$IMGFMT" = "qed" \) -a -n "$CLUSTER_SIZE" ]; then
-        extra_img_options="-o cluster_size=$CLUSTER_SIZE $extra_img_options"
-        cluster_size_filter=""
+        optstr=$(_optstr_add "$optstr" "cluster_size=$CLUSTER_SIZE")
+    fi
+
+    if [ -n "$optstr" ]; then
+        extra_img_options="-o $optstr $extra_img_options"
     fi
 
     # XXX(hch): have global image options?
@@ -76,8 +99,9 @@ _make_test_img()
     	sed -e "s#$TEST_DIR#TEST_DIR#g" | \
     	sed -e "s#$IMGFMT#IMGFMT#g" | \
 	sed -e "s# encryption=off##g" | \
-	sed -e "$cluster_size_filter" | \
+	sed -e "s# cluster_size=[0-9]\\+##g" | \
 	sed -e "s# table_size=0##g" | \
+	sed -e "s# compat='[^']*'##g" | \
 	sed -e "s# compat6=off##g" | \
 	sed -e "s# static=off##g"
 }
@@ -270,7 +294,11 @@ _require_command()
 
 _full_imgfmt_details()
 {
-    echo "$IMGFMT"
+    if [ -n "$IMGOPTS" ]; then
+        echo "$IMGFMT ($IMGOPTS)"
+    else
+        echo "$IMGFMT"
+    fi
 }
 
 _full_imgproto_details()
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 1742ede..5934829 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -38,3 +38,6 @@
 029 rw auto quick
 030 rw auto
 031 rw auto quick
+032 rw auto
+033 rw auto
+034 rw auto backing
diff --git a/tests/qemu-iotests/qcow2.py b/tests/qemu-iotests/qcow2.py
index bfb47e8..e27196a 100755
--- a/tests/qemu-iotests/qcow2.py
+++ b/tests/qemu-iotests/qcow2.py
@@ -35,6 +35,13 @@ class QcowHeader:
         [ uint32_t, '%d',   'refcount_table_clusters' ],
         [ uint32_t, '%d',   'nb_snapshots' ],
         [ uint64_t, '%#x',  'snapshot_offset' ],
+
+        # Version 3 header fields
+        [ uint64_t, '%#x',  'incompatible_features' ],
+        [ uint64_t, '%#x',  'compatible_features' ],
+        [ uint64_t, '%#x',  'autoclear_features' ],
+        [ uint32_t, '%d',   'refcount_order' ],
+        [ uint32_t, '%d',   'header_length' ],
     ];
 
     fmt = '>' + ''.join(field[0] for field in fields)
@@ -50,9 +57,10 @@ class QcowHeader:
         self.__dict__ = dict((field[2], header[i])
             for i, field in enumerate(QcowHeader.fields))
 
+        self.set_defaults()
         self.cluster_size = 1 << self.cluster_bits
 
-        fd.seek(self.get_header_length())
+        fd.seek(self.header_length)
         self.load_extensions(fd)
 
         if self.backing_file_offset:
@@ -61,11 +69,13 @@ class QcowHeader:
         else:
             self.backing_file = None
 
-    def get_header_length(self):
+    def set_defaults(self):
         if self.version == 2:
-            return 72
-        else:
-            raise Exception("version != 2 not supported")
+            self.incompatible_features = 0
+            self.compatible_features = 0
+            self.autoclear_features = 0
+            self.refcount_order = 4
+            self.header_length = 72
 
     def load_extensions(self, fd):
         self.extensions = []
@@ -86,7 +96,7 @@ class QcowHeader:
 
     def update_extensions(self, fd):
 
-        fd.seek(self.get_header_length())
+        fd.seek(self.header_length)
         extensions = self.extensions
         extensions.append(QcowHeaderExtension(0, 0, ""))
         for ex in extensions:
@@ -103,7 +113,7 @@ class QcowHeader:
 
 
     def update(self, fd):
-        header_bytes = self.get_header_length()
+        header_bytes = self.header_length
 
         self.update_extensions(fd)