1 files changed, 269 insertions, 0 deletions
diff --git a/block/stream.c b/block/stream.c
new file mode 100644
index 0000000..d1b3986
--- /dev/null
+++ b/block/stream.c
@@ -0,0 +1,269 @@
+/*
+ * Image streaming
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include "trace.h"
+#include "block_int.h"
+
+enum {
+    /*
+     * Size of data buffer for populating the image file.  This should be large
+     * enough to process multiple clusters in a single call, so that populating
+     * contiguous regions of the image is efficient.
+     */
+    STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
+};
+
+#define SLICE_TIME 100000000ULL /* ns */
+
+typedef struct {
+    int64_t next_slice_time;
+    uint64_t slice_quota;
+    uint64_t dispatched;
+} RateLimit;
+
+static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
+{
+    int64_t delay_ns = 0;
+    int64_t now = qemu_get_clock_ns(rt_clock);
+
+    if (limit->next_slice_time < now) {
+        limit->next_slice_time = now + SLICE_TIME;
+        limit->dispatched = 0;
+    }
+    if (limit->dispatched + n > limit->slice_quota) {
+        delay_ns = limit->next_slice_time - now;
+    } else {
+        limit->dispatched += n;
+    }
+    return delay_ns;
+}
+
+static void ratelimit_set_speed(RateLimit *limit, uint64_t speed)
+{
+    limit->slice_quota = speed / (1000000000ULL / SLICE_TIME);
+}
+
+typedef struct StreamBlockJob {
+    BlockJob common;
+    RateLimit limit;
+    BlockDriverState *base;
+    char backing_file_id[1024];
+} StreamBlockJob;
+
+static int coroutine_fn stream_populate(BlockDriverState *bs,
+                                        int64_t sector_num, int nb_sectors,
+                                        void *buf)
+{
+    struct iovec iov = {
+        .iov_base = buf,
+        .iov_len  = nb_sectors * BDRV_SECTOR_SIZE,
+    };
+    QEMUIOVector qiov;
+
+    qemu_iovec_init_external(&qiov, &iov, 1);
+
+    /* Copy-on-read the unallocated clusters */
+    return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov);
+}
+
+/*
+ * Given an image chain: [BASE] -> [INTER1] -> [INTER2] -> [TOP]
+ *
+ * Return true if the given sector is allocated in top.
+ * Return false if the given sector is allocated in intermediate images.
+ * Return true otherwise.
+ *
+ * 'pnum' is set to the number of sectors (including and immediately following
+ *  the specified sector) that are known to be in the same
+ *  allocated/unallocated state.
+ *
+ */
+static int coroutine_fn is_allocated_base(BlockDriverState *top,
+                                          BlockDriverState *base,
+                                          int64_t sector_num,
+                                          int nb_sectors, int *pnum)
+{
+    BlockDriverState *intermediate;
+    int ret, n;
+
+    ret = bdrv_co_is_allocated(top, sector_num, nb_sectors, &n);
+    if (ret) {
+        *pnum = n;
+        return ret;
+    }
+
+    /*
+     * Is the unallocated chunk [sector_num, n] also
+     * unallocated between base and top?
+     */
+    intermediate = top->backing_hd;
+
+    while (intermediate) {
+        int pnum_inter;
+
+        /* reached base */
+        if (intermediate == base) {
+            *pnum = n;
+            return 1;
+        }
+        ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors,
+                                   &pnum_inter);
+        if (ret < 0) {
+            return ret;
+        } else if (ret) {
+            *pnum = pnum_inter;
+            return 0;
+        }
+
+        /*
+         * [sector_num, nb_sectors] is unallocated on top but intermediate
+         * might have
+         *
+         * [sector_num+x, nr_sectors] allocated.
+         */
+        if (n > pnum_inter) {
+            n = pnum_inter;
+        }
+
+        intermediate = intermediate->backing_hd;
+    }
+
+    return 1;
+}
+
+static void coroutine_fn stream_run(void *opaque)
+{
+    StreamBlockJob *s = opaque;
+    BlockDriverState *bs = s->common.bs;
+    BlockDriverState *base = s->base;
+    int64_t sector_num, end;
+    int ret = 0;
+    int n;
+    void *buf;
+
+    s->common.len = bdrv_getlength(bs);
+    if (s->common.len < 0) {
+        block_job_complete(&s->common, s->common.len);
+        return;
+    }
+
+    end = s->common.len >> BDRV_SECTOR_BITS;
+    buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
+
+    /* Turn on copy-on-read for the whole block device so that guest read
+     * requests help us make progress.  Only do this when copying the entire
+     * backing chain since the copy-on-read operation does not take base into
+     * account.
+     */
+    if (!base) {
+        bdrv_enable_copy_on_read(bs);
+    }
+
+    for (sector_num = 0; sector_num < end; sector_num += n) {
+retry:
+        if (block_job_is_cancelled(&s->common)) {
+            break;
+        }
+
+
+        if (base) {
+            ret = is_allocated_base(bs, base, sector_num,
+                                    STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
+        } else {
+            ret = bdrv_co_is_allocated(bs, sector_num,
+                                       STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE,
+                                       &n);
+        }
+        trace_stream_one_iteration(s, sector_num, n, ret);
+        if (ret == 0) {
+            if (s->common.speed) {
+                uint64_t delay_ns = ratelimit_calculate_delay(&s->limit, n);
+                if (delay_ns > 0) {
+                    co_sleep_ns(rt_clock, delay_ns);
+
+                    /* Recheck cancellation and that sectors are unallocated */
+                    goto retry;
+                }
+            }
+            ret = stream_populate(bs, sector_num, n, buf);
+        }
+        if (ret < 0) {
+            break;
+        }
+        ret = 0;
+
+        /* Publish progress */
+        s->common.offset += n * BDRV_SECTOR_SIZE;
+
+        /* Note that even when no rate limit is applied we need to yield
+         * with no pending I/O here so that qemu_aio_flush() returns.
+         */
+        co_sleep_ns(rt_clock, 0);
+    }
+
+    if (!base) {
+        bdrv_disable_copy_on_read(bs);
+    }
+
+    if (sector_num == end && ret == 0) {
+        const char *base_id = NULL;
+        if (base) {
+            base_id = s->backing_file_id;
+        }
+        ret = bdrv_change_backing_file(bs, base_id, NULL);
+    }
+
+    qemu_vfree(buf);
+    block_job_complete(&s->common, ret);
+}
+
+static int stream_set_speed(BlockJob *job, int64_t value)
+{
+    StreamBlockJob *s = container_of(job, StreamBlockJob, common);
+
+    if (value < 0) {
+        return -EINVAL;
+    }
+    job->speed = value;
+    ratelimit_set_speed(&s->limit, value / BDRV_SECTOR_SIZE);
+    return 0;
+}
+
+static BlockJobType stream_job_type = {
+    .instance_size = sizeof(StreamBlockJob),
+    .job_type      = "stream",
+    .set_speed     = stream_set_speed,
+};
+
+int stream_start(BlockDriverState *bs, BlockDriverState *base,
+                 const char *base_id, BlockDriverCompletionFunc *cb,
+                 void *opaque)
+{
+    StreamBlockJob *s;
+    Coroutine *co;
+
+    s = block_job_create(&stream_job_type, bs, cb, opaque);
+    if (!s) {
+        return -EBUSY; /* bs must already be in use */
+    }
+
+    s->base = base;
+    if (base_id) {
+        pstrcpy(s->backing_file_id, sizeof(s->backing_file_id), base_id);
+    }
+
+    co = qemu_coroutine_create(stream_run);
+    trace_stream_start(bs, base, s, co, opaque);
+    qemu_coroutine_enter(co, s);
+    return 0;
+}