/* * Block driver for the QCOW version 2 format * * Copyright (c) 2004-2006 Fabrice Bellard * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include #include "qemu-common.h" #include "block/block_int.h" #include "block/qcow2.h" #include "trace.h" int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, bool exact_size) { BDRVQcowState *s = bs->opaque; int new_l1_size2, ret, i; uint64_t *new_l1_table; int64_t old_l1_table_offset, old_l1_size; int64_t new_l1_table_offset, new_l1_size; uint8_t data[12]; if (min_size <= s->l1_size) return 0; if (exact_size) { new_l1_size = min_size; } else { /* Bump size up to reduce the number of times we have to grow */ new_l1_size = s->l1_size; if (new_l1_size == 0) { new_l1_size = 1; } while (min_size > new_l1_size) { new_l1_size = (new_l1_size * 3 + 1) / 2; } } if (new_l1_size > INT_MAX / sizeof(uint64_t)) { return -EFBIG; } #ifdef DEBUG_ALLOC2 fprintf(stderr, "grow l1_table from %d to %" PRId64 "\n", s->l1_size, new_l1_size); #endif new_l1_size2 = sizeof(uint64_t) * new_l1_size; new_l1_table = g_malloc0(align_offset(new_l1_size2, 512)); memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t)); /* write new table (align to cluster) */ BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ALLOC_TABLE); new_l1_table_offset = qcow2_alloc_clusters(bs, new_l1_size2); if (new_l1_table_offset < 0) { g_free(new_l1_table); return new_l1_table_offset; } ret = qcow2_cache_flush(bs, s->refcount_block_cache); if (ret < 0) { goto fail; } /* the L1 position has not yet been updated, so these clusters must * indeed be completely free */ ret = qcow2_pre_write_overlap_check(bs, 0, new_l1_table_offset, new_l1_size2); if (ret < 0) { goto fail; } BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_WRITE_TABLE); for(i = 0; i < s->l1_size; i++) new_l1_table[i] = cpu_to_be64(new_l1_table[i]); ret = bdrv_pwrite_sync(bs->file, new_l1_table_offset, new_l1_table, new_l1_size2); if (ret < 0) goto fail; for(i = 0; i < s->l1_size; i++) new_l1_table[i] = be64_to_cpu(new_l1_table[i]); /* set new table */ BLKDBG_EVENT(bs->file, BLKDBG_L1_GROW_ACTIVATE_TABLE); cpu_to_be32w((uint32_t*)data, new_l1_size); stq_be_p(data + 4, new_l1_table_offset); ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, l1_size), data,sizeof(data)); if (ret < 0) { goto fail; } g_free(s->l1_table); old_l1_table_offset = s->l1_table_offset; s->l1_table_offset = new_l1_table_offset; s->l1_table = new_l1_table; old_l1_size = s->l1_size; s->l1_size = new_l1_size; qcow2_free_clusters(bs, old_l1_table_offset, old_l1_size * sizeof(uint64_t), QCOW2_DISCARD_OTHER); return 0; fail: g_free(new_l1_table); qcow2_free_clusters(bs, new_l1_table_offset, new_l1_size2, QCOW2_DISCARD_OTHER); return ret; } /* * l2_load * * Loads a L2 table into memory. If the table is in the cache, the cache * is used; otherwise the L2 table is loaded from the image file. * * Returns a pointer to the L2 table on success, or NULL if the read from * the image file failed. */ static int l2_load(BlockDriverState *bs, uint64_t l2_offset, uint64_t **l2_table) { BDRVQcowState *s = bs->opaque; int ret; ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, (void**) l2_table); return ret; } /* * Writes one sector of the L1 table to the disk (can't update single entries * and we really don't want bdrv_pread to perform a read-modify-write) */ #define L1_ENTRIES_PER_SECTOR (512 / 8) int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index) { BDRVQcowState *s = bs->opaque; uint64_t buf[L1_ENTRIES_PER_SECTOR]; int l1_start_index; int i, ret; l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1); for (i = 0; i < L1_ENTRIES_PER_SECTOR; i++) { buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]); } ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1, s->l1_table_offset + 8 * l1_start_index, sizeof(buf)); if (ret < 0) { return ret; } BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE); ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset + 8 * l1_start_index, buf, sizeof(buf)); if (ret < 0) { return ret; } return 0; } /* * l2_allocate * * Allocate a new l2 entry in the file. If l1_index points to an already * used entry in the L2 table (i.e. we are doing a copy on write for the L2 * table) copy the contents of the old L2 table into the newly allocated one. * Otherwise the new table is initialized with zeros. * */ static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table) { BDRVQcowState *s = bs->opaque; uint64_t old_l2_offset; uint64_t *l2_table = NULL; int64_t l2_offset; int ret; old_l2_offset = s->l1_table[l1_index]; trace_qcow2_l2_allocate(bs, l1_index); /* allocate a new l2 entry */ l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t)); if (l2_offset < 0) { ret = l2_offset; goto fail; } ret = qcow2_cache_flush(bs, s->refcount_block_cache); if (ret < 0) { goto fail; } /* allocate a new entry in the l2 cache */ trace_qcow2_l2_allocate_get_empty(bs, l1_index); ret = qcow2_cache_get_empty(bs, s->l2_table_cache, l2_offset, (void**) table); if (ret < 0) { goto fail; } l2_table = *table; 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 { uint64_t* old_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 & L1E_OFFSET_MASK, (void**) &old_table); if (ret < 0) { goto fail; } memcpy(l2_table, old_table, s->cluster_size); ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &old_table); if (ret < 0) { goto fail; } } /* write the l2 table to the file */ BLKDBG_EVENT(bs->file, BLKDBG_L2_ALLOC_WRITE); trace_qcow2_l2_allocate_write_l2(bs, l1_index); qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); ret = qcow2_cache_flush(bs, s->l2_table_cache); if (ret < 0) { goto fail; } /* update the L1 entry */ trace_qcow2_l2_allocate_write_l1(bs, l1_index); s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED; ret = qcow2_write_l1_entry(bs, l1_index); if (ret < 0) { goto fail; } *table = l2_table; trace_qcow2_l2_allocate_done(bs, l1_index, 0); return 0; fail: trace_qcow2_l2_allocate_done(bs, l1_index, ret); if (l2_table != NULL) { qcow2_cache_put(bs, s->l2_table_cache, (void**) table); } s->l1_table[l1_index] = old_l2_offset; if (l2_offset > 0) { qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), QCOW2_DISCARD_ALWAYS); } 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 stop_flags) { int i; uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED; uint64_t first_entry = be64_to_cpu(l2_table[0]); uint64_t offset = first_entry & mask; if (!offset) return 0; assert(qcow2_get_cluster_type(first_entry) != QCOW2_CLUSTER_COMPRESSED); for (i = 0; i < 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; } static int count_contiguous_free_clusters(uint64_t nb_clusters, uint64_t *l2_table) { int i; for (i = 0; i < nb_clusters; i++) { int type = qcow2_get_cluster_type(be64_to_cpu(l2_table[i])); if (type != QCOW2_CLUSTER_UNALLOCATED) { break; } } return i; } /* The crypt function is compatible with the linux cryptoloop algorithm for < 4 GB images. NOTE: out_buf == in_buf is supported */ void qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num, uint8_t *out_buf, const uint8_t *in_buf, int nb_sectors, int enc, const AES_KEY *key) { union { uint64_t ll[2]; uint8_t b[16]; } ivec; int i; for(i = 0; i < nb_sectors; i++) { ivec.ll[0] = cpu_to_le64(sector_num); ivec.ll[1] = 0; AES_cbc_encrypt(in_buf, out_buf, 512, key, ivec.b, enc); sector_num++; in_buf += 512; out_buf += 512; } } static int coroutine_fn copy_sectors(BlockDriverState *bs, uint64_t start_sect, uint64_t cluster_offset, int n_start, int n_end) { BDRVQcowState *s = bs->opaque; QEMUIOVector qiov; struct iovec iov; int n, ret; /* * If this is the last cluster and it is only partially used, we must only * copy until the end of the image, or bdrv_check_request will fail for the * bdrv_read/write calls below. */ if (start_sect + n_end > bs->total_sectors) { n_end = bs->total_sectors - start_sect; } n = n_end - n_start; if (n <= 0) { return 0; } iov.iov_len = n * BDRV_SECTOR_SIZE; iov.iov_base = qemu_blockalign(bs, iov.iov_len); qemu_iovec_init_external(&qiov, &iov, 1); BLKDBG_EVENT(bs->file, BLKDBG_COW_READ); if (!bs->drv) { return -ENOMEDIUM; } /* Call .bdrv_co_readv() directly instead of using the public block-layer * interface. This avoids double I/O throttling and request tracking, * which can lead to deadlock when block layer copy-on-read is enabled. */ ret = bs->drv->bdrv_co_readv(bs, start_sect + n_start, n, &qiov); if (ret < 0) { goto out; } if (s->crypt_method) { qcow2_encrypt_sectors(s, start_sect + n_start, iov.iov_base, iov.iov_base, n, 1, &s->aes_encrypt_key); } ret = qcow2_pre_write_overlap_check(bs, 0, cluster_offset + n_start * BDRV_SECTOR_SIZE, n * BDRV_SECTOR_SIZE); if (ret < 0) { goto out; } BLKDBG_EVENT(bs->file, BLKDBG_COW_WRITE); ret = bdrv_co_writev(bs->file, (cluster_offset >> 9) + n_start, n, &qiov); if (ret < 0) { goto out; } ret = 0; out: qemu_vfree(iov.iov_base); return ret; } /* * get_cluster_offset * * For a given offset of the disk image, find the cluster offset in * qcow2 file. The offset is stored in *cluster_offset. * * on entry, *num is the number of contiguous sectors we'd like to * access following offset. * * on exit, *num is the number of contiguous sectors we can read. * * 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) { BDRVQcowState *s = bs->opaque; unsigned int l2_index; uint64_t l1_index, l2_offset, *l2_table; int l1_bits, c; unsigned int index_in_cluster, nb_clusters; uint64_t nb_available, nb_needed; int ret; index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1); nb_needed = *num + index_in_cluster; l1_bits = s->l2_bits + s->cluster_bits; /* compute how many bytes there are between the offset and * the end of the l1 entry */ nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1)); /* compute the number of available sectors */ nb_available = (nb_available >> 9) + index_in_cluster; if (nb_needed > nb_available) { nb_needed = nb_available; } *cluster_offset = 0; /* seek the the l2 offset in the l1 table */ l1_index = offset >> l1_bits; if (l1_index >= s->l1_size) { ret = QCOW2_CLUSTER_UNALLOCATED; goto out; } 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 */ ret = l2_load(bs, l2_offset, &l2_table); if (ret < 0) { return ret; } /* find the cluster offset for the given disk offset */ l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1); *cluster_offset = be64_to_cpu(l2_table[l2_index]); nb_clusters = size_to_clusters(s, nb_needed << 9); 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: if (s->qcow_version < 3) { return -EIO; } c = count_contiguous_clusters(nb_clusters, s->cluster_size, &l2_table[l2_index], 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]); *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], QCOW_OFLAG_ZERO); *cluster_offset &= L2E_OFFSET_MASK; break; default: abort(); } qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); nb_available = (c * s->cluster_sectors); out: if (nb_available > nb_needed) nb_available = nb_needed; *num = nb_available - index_in_cluster; return ret; } /* * get_cluster_table * * for a given disk offset, load (and allocate if needed) * the l2 table. * * the l2 table offset in the qcow2 file and the cluster index * in the l2 table are given to the caller. * * Returns 0 on success, -errno in failure case */ static int get_cluster_table(BlockDriverState *bs, uint64_t offset, uint64_t **new_l2_table, int *new_l2_index) { BDRVQcowState *s = bs->opaque; unsigned int l2_index; uint64_t l1_index, l2_offset; uint64_t *l2_table = NULL; int ret; /* seek the the l2 offset in the l1 table */ l1_index = offset >> (s->l2_bits + s->cluster_bits); if (l1_index >= s->l1_size) { ret = qcow2_grow_l1_table(bs, l1_index + 1, false); if (ret < 0) { return ret; } } assert(l1_index < s->l1_size); l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK; /* seek the l2 table of the given l2 offset */ if (s->l1_table[l1_index] & QCOW_OFLAG_COPIED) { /* load the l2 table in memory */ ret = l2_load(bs, l2_offset, &l2_table); if (ret < 0) { return ret; } } else { /* First allocate a new L2 table (and do COW if needed) */ ret = l2_allocate(bs, l1_index, &l2_table); if (ret < 0) { return ret; } /* Then decrease the refcount of the old table */ if (l2_offset) { qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t), QCOW2_DISCARD_OTHER); } } /* find the cluster offset for the given disk offset */ l2_index = (offset >> s->cluster_bits) & (s->l2_size - 1); *new_l2_table = l2_table; *new_l2_index = l2_index; return 0; } /* * alloc_compressed_cluster_offset * * For a given offset of the disk image, return cluster offset in * qcow2 file. * * If the offset is not found, allocate a new compressed cluster. * * Return the cluster offset if successful, * Return 0, otherwise. * */ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, uint64_t offset, int compressed_size) { BDRVQcowState *s = bs->opaque; int l2_index, ret; uint64_t *l2_table; int64_t cluster_offset; int nb_csectors; ret = get_cluster_table(bs, offset, &l2_table, &l2_index); if (ret < 0) { 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 & L2E_OFFSET_MASK) { qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); return 0; } cluster_offset = qcow2_alloc_bytes(bs, compressed_size); if (cluster_offset < 0) { qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); return 0; } nb_csectors = ((cluster_offset + compressed_size - 1) >> 9) - (cluster_offset >> 9); cluster_offset |= QCOW_OFLAG_COMPRESSED | ((uint64_t)nb_csectors << s->csize_shift); /* update L2 table */ /* compressed clusters never have the copied flag */ BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE_COMPRESSED); qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); l2_table[l2_index] = cpu_to_be64(cluster_offset); ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); if (ret < 0) { return 0; } return cluster_offset; } static int perform_cow(BlockDriverState *bs, QCowL2Meta *m, Qcow2COWRegion *r) { BDRVQcowState *s = bs->opaque; int ret; if (r->nb_sectors == 0) { return 0; } qemu_co_mutex_unlock(&s->lock); ret = copy_sectors(bs, m->offset / BDRV_SECTOR_SIZE, m->alloc_offset, r->offset / BDRV_SECTOR_SIZE, r->offset / BDRV_SECTOR_SIZE + r->nb_sectors); qemu_co_mutex_lock(&s->lock); if (ret < 0) { return ret; } /* * Before we update the L2 table to actually point to the new cluster, we * need to be sure that the refcounts have been increased and COW was * handled. */ qcow2_cache_depends_on_flush(s->l2_table_cache); return 0; } int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) { BDRVQcowState *s = bs->opaque; int i, j = 0, l2_index, ret; uint64_t *old_cluster, *l2_table; uint64_t cluster_offset = m->alloc_offset; trace_qcow2_cluster_link_l2(qemu_coroutine_self(), m->nb_clusters); assert(m->nb_clusters > 0); old_cluster = g_malloc(m->nb_clusters * sizeof(uint64_t)); /* copy content of unmodified sectors */ ret = perform_cow(bs, m, &m->cow_start); if (ret < 0) { goto err; } ret = perform_cow(bs, m, &m->cow_end); if (ret < 0) { goto err; } /* Update L2 table. */ if (s->use_lazy_refcounts) { qcow2_mark_dirty(bs); } if (qcow2_need_accurate_refcounts(s)) { qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache); } ret = get_cluster_table(bs, m->offset, &l2_table, &l2_index); if (ret < 0) { goto err; } qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); assert(l2_index + m->nb_clusters <= s->l2_size); for (i = 0; i < m->nb_clusters; i++) { /* if two concurrent writes happen to the same unallocated cluster * each write allocates separate cluster and writes data concurrently. * The first one to complete updates l2 table with pointer to its * cluster the second one has to do RMW (which is done above by * copy_sectors()), update l2 table with its cluster pointer and free * old cluster. This is what this loop does */ if(l2_table[l2_index + i] != 0) old_cluster[j++] = l2_table[l2_index + i]; l2_table[l2_index + i] = cpu_to_be64((cluster_offset + (i << s->cluster_bits)) | QCOW_OFLAG_COPIED); } ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); if (ret < 0) { goto err; } /* * If this was a COW, we need to decrease the refcount of the old cluster. * Also flush bs->file to get the right order for L2 and refcount update. * * Don't discard clusters that reach a refcount of 0 (e.g. compressed * clusters), the next write will reuse them anyway. */ if (j != 0) { for (i = 0; i < j; i++) { qcow2_free_any_clusters(bs, be64_to_cpu(old_cluster[i]), 1, QCOW2_DISCARD_NEVER); } } ret = 0; err: g_free(old_cluster); return ret; } /* * Returns the number of contiguous clusters that can be used for an allocating * write, but require COW to be performed (this includes yet unallocated space, * which must copy from the backing file) */ static int count_cow_clusters(BDRVQcowState *s, int nb_clusters, uint64_t *l2_table, int l2_index) { int i; 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); switch(cluster_type) { case QCOW2_CLUSTER_NORMAL: if (l2_entry & QCOW_OFLAG_COPIED) { goto out; } break; case QCOW2_CLUSTER_UNALLOCATED: case QCOW2_CLUSTER_COMPRESSED: case QCOW2_CLUSTER_ZERO: break; default: abort(); } } out: assert(i <= nb_clusters); return i; } /* * Check if there already is an AIO write request in flight which allocates * the same cluster. In this case we need to wait until the previous * request has completed and updated the L2 table accordingly. * * Returns: * 0 if there was no dependency. *cur_bytes indicates the number of * bytes from guest_offset that can be read before the next * dependency must be processed (or the request is complete) * * -EAGAIN if we had to wait for another request, previously gathered * information on cluster allocation may be invalid now. The caller * must start over anyway, so consider *cur_bytes undefined. */ static int handle_dependencies(BlockDriverState *bs, uint64_t guest_offset, uint64_t *cur_bytes, QCowL2Meta **m) { BDRVQcowState *s = bs->opaque; QCowL2Meta *old_alloc; uint64_t bytes = *cur_bytes; QLIST_FOREACH(old_alloc, &s->cluster_allocs, next_in_flight) { uint64_t start = guest_offset; uint64_t end = start + bytes; uint64_t old_start = l2meta_cow_start(old_alloc); uint64_t old_end = l2meta_cow_end(old_alloc); if (end <= old_start || start >= old_end) { /* No intersection */ } else { if (start < old_start) { /* Stop at the start of a running allocation */ bytes = old_start - start; } else { bytes = 0; } /* Stop if already an l2meta exists. After yielding, it wouldn't * be valid any more, so we'd have to clean up the old L2Metas * and deal with requests depending on them before starting to * gather new ones. Not worth the trouble. */ if (bytes == 0 && *m) { *cur_bytes = 0; return 0; } if (bytes == 0) { /* Wait for the dependency to complete. We need to recheck * the free/allocated clusters when we continue. */ qemu_co_mutex_unlock(&s->lock); qemu_co_queue_wait(&old_alloc->dependent_requests); qemu_co_mutex_lock(&s->lock); return -EAGAIN; } } } /* Make sure that existing clusters and new allocations are only used up to * the next dependency if we shortened the request above */ *cur_bytes = bytes; return 0; } /* * Checks how many already allocated clusters that don't require a copy on * write there are at the given guest_offset (up to *bytes). If * *host_offset is not zero, only physically contiguous clusters beginning at * this host offset are counted. * * Note that guest_offset may not be cluster aligned. In this case, the * returned *host_offset points to exact byte referenced by guest_offset and * therefore isn't cluster aligned as well. * * Returns: * 0: if no allocated clusters are available at the given offset. * *bytes is normally unchanged. It is set to 0 if the cluster * is allocated and doesn't need COW, but doesn't have the right * physical offset. * * 1: if allocated clusters that don't require a COW are available at * the requested offset. *bytes may have decreased and describes * the length of the area that can be written to. * * -errno: in error cases */ static int handle_copied(BlockDriverState *bs, uint64_t guest_offset, uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) { BDRVQcowState *s = bs->opaque; int l2_index; uint64_t cluster_offset; uint64_t *l2_table; unsigned int nb_clusters; unsigned int keep_clusters; int ret, pret; trace_qcow2_handle_copied(qemu_coroutine_self(), guest_offset, *host_offset, *bytes); assert(*host_offset == 0 || offset_into_cluster(s, guest_offset) == offset_into_cluster(s, *host_offset)); /* * Calculate the number of clusters to look for. We stop at L2 table * boundaries to keep things simple. */ nb_clusters = size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); l2_index = offset_to_l2_index(s, guest_offset); nb_clusters = MIN(nb_clusters, s->l2_size - l2_index); /* Find L2 entry for the first involved cluster */ ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index); if (ret < 0) { return ret; } cluster_offset = be64_to_cpu(l2_table[l2_index]); /* Check how many clusters are already allocated and don't need COW */ if (qcow2_get_cluster_type(cluster_offset) == QCOW2_CLUSTER_NORMAL && (cluster_offset & QCOW_OFLAG_COPIED)) { /* If a specific host_offset is required, check it */ bool offset_matches = (cluster_offset & L2E_OFFSET_MASK) == *host_offset; if (*host_offset != 0 && !offset_matches) { *bytes = 0; ret = 0; goto out; } /* We keep all QCOW_OFLAG_COPIED clusters */ keep_clusters = count_contiguous_clusters(nb_clusters, s->cluster_size, &l2_table[l2_index], QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO); assert(keep_clusters <= nb_clusters); *bytes = MIN(*bytes, keep_clusters * s->cluster_size - offset_into_cluster(s, guest_offset)); ret = 1; } else { ret = 0; } /* Cleanup */ out: pret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); if (pret < 0) { return pret; } /* Only return a host offset if we actually made progress. Otherwise we * would make requirements for handle_alloc() that it can't fulfill */ if (ret) { *host_offset = (cluster_offset & L2E_OFFSET_MASK) + offset_into_cluster(s, guest_offset); } return ret; } /* * Allocates new clusters for the given guest_offset. * * At most *nb_clusters are allocated, and on return *nb_clusters is updated to * contain the number of clusters that have been allocated and are contiguous * in the image file. * * If *host_offset is non-zero, it specifies the offset in the image file at * which the new clusters must start. *nb_clusters can be 0 on return in this * case if the cluster at host_offset is already in use. If *host_offset is * zero, the clusters can be allocated anywhere in the image file. * * *host_offset is updated to contain the offset into the image file at which * the first allocated cluster starts. * * Return 0 on success and -errno in error cases. -EAGAIN means that the * function has been waiting for another request and the allocation must be * restarted, but the whole request should not be failed. */ static int do_alloc_cluster_offset(BlockDriverState *bs, uint64_t guest_offset, uint64_t *host_offset, unsigned int *nb_clusters) { BDRVQcowState *s = bs->opaque; trace_qcow2_do_alloc_clusters_offset(qemu_coroutine_self(), guest_offset, *host_offset, *nb_clusters); /* Allocate new clusters */ trace_qcow2_cluster_alloc_phys(qemu_coroutine_self()); if (*host_offset == 0) { int64_t cluster_offset = qcow2_alloc_clusters(bs, *nb_clusters * s->cluster_size); if (cluster_offset < 0) { return cluster_offset; } *host_offset = cluster_offset; return 0; } else { int ret = qcow2_alloc_clusters_at(bs, *host_offset, *nb_clusters); if (ret < 0) { return ret; } *nb_clusters = ret; return 0; } } /* * Allocates new clusters for an area that either is yet unallocated or needs a * copy on write. If *host_offset is non-zero, clusters are only allocated if * the new allocation can match the specified host offset. * * Note that guest_offset may not be cluster aligned. In this case, the * returned *host_offset points to exact byte referenced by guest_offset and * therefore isn't cluster aligned as well. * * Returns: * 0: if no clusters could be allocated. *bytes is set to 0, * *host_offset is left unchanged. * * 1: if new clusters were allocated. *bytes may be decreased if the * new allocation doesn't cover all of the requested area. * *host_offset is updated to contain the host offset of the first * newly allocated cluster. * * -errno: in error cases */ static int handle_alloc(BlockDriverState *bs, uint64_t guest_offset, uint64_t *host_offset, uint64_t *bytes, QCowL2Meta **m) { BDRVQcowState *s = bs->opaque; int l2_index; uint64_t *l2_table; uint64_t entry; unsigned int nb_clusters; int ret; uint64_t alloc_cluster_offset; trace_qcow2_handle_alloc(qemu_coroutine_self(), guest_offset, *host_offset, *bytes); assert(*bytes > 0); /* * Calculate the number of clusters to look for. We stop at L2 table * boundaries to keep things simple. */ nb_clusters = size_to_clusters(s, offset_into_cluster(s, guest_offset) + *bytes); l2_index = offset_to_l2_index(s, guest_offset); nb_clusters = MIN(nb_clusters, s->l2_size - l2_index); /* Find L2 entry for the first involved cluster */ ret = get_cluster_table(bs, guest_offset, &l2_table, &l2_index); if (ret < 0) { return ret; } entry = be64_to_cpu(l2_table[l2_index]); /* For the moment, overwrite compressed clusters one by one */ if (entry & QCOW_OFLAG_COMPRESSED) { nb_clusters = 1; } else { nb_clusters = count_cow_clusters(s, nb_clusters, l2_table, l2_index); } /* This function is only called when there were no non-COW clusters, so if * we can't find any unallocated or COW clusters either, something is * wrong with our code. */ assert(nb_clusters > 0); ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); if (ret < 0) { return ret; } /* Allocate, if necessary at a given offset in the image file */ alloc_cluster_offset = start_of_cluster(s, *host_offset); ret = do_alloc_cluster_offset(bs, guest_offset, &alloc_cluster_offset, &nb_clusters); if (ret < 0) { goto fail; } /* Can't extend contiguous allocation */ if (nb_clusters == 0) { *bytes = 0; return 0; } /* * Save info needed for meta data update. * * requested_sectors: Number of sectors from the start of the first * newly allocated cluster to the end of the (possibly shortened * before) write request. * * avail_sectors: Number of sectors from the start of the first * newly allocated to the end of the last newly allocated cluster. * * nb_sectors: The number of sectors from the start of the first * newly allocated cluster to the end of the area that the write * request actually writes to (excluding COW at the end) */ int requested_sectors = (*bytes + offset_into_cluster(s, guest_offset)) >> BDRV_SECTOR_BITS; int avail_sectors = nb_clusters << (s->cluster_bits - BDRV_SECTOR_BITS); int alloc_n_start = offset_into_cluster(s, guest_offset) >> BDRV_SECTOR_BITS; int nb_sectors = MIN(requested_sectors, avail_sectors); QCowL2Meta *old_m = *m; *m = g_malloc0(sizeof(**m)); **m = (QCowL2Meta) { .next = old_m, .alloc_offset = alloc_cluster_offset, .offset = start_of_cluster(s, guest_offset), .nb_clusters = nb_clusters, .nb_available = nb_sectors, .cow_start = { .offset = 0, .nb_sectors = alloc_n_start, }, .cow_end = { .offset = nb_sectors * BDRV_SECTOR_SIZE, .nb_sectors = avail_sectors - nb_sectors, }, }; qemu_co_queue_init(&(*m)->dependent_requests); QLIST_INSERT_HEAD(&s->cluster_allocs, *m, next_in_flight); *host_offset = alloc_cluster_offset + offset_into_cluster(s, guest_offset); *bytes = MIN(*bytes, (nb_sectors * BDRV_SECTOR_SIZE) - offset_into_cluster(s, guest_offset)); assert(*bytes != 0); return 1; fail: if (*m && (*m)->nb_clusters > 0) { QLIST_REMOVE(*m, next_in_flight); } return ret; } /* * alloc_cluster_offset * * For a given offset on the virtual disk, find the cluster offset in qcow2 * file. If the offset is not found, allocate a new cluster. * * If the cluster was already allocated, m->nb_clusters is set to 0 and * other fields in m are meaningless. * * If the cluster is newly allocated, m->nb_clusters is set to the number of * contiguous clusters that have been allocated. In this case, the other * fields of m are valid and contain information about the first allocated * cluster. * * If the request conflicts with another write request in flight, the coroutine * is queued and will be reentered when the dependency has completed. * * Return 0 on success and -errno in error cases */ int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset, int *num, uint64_t *host_offset, QCowL2Meta **m) { BDRVQcowState *s = bs->opaque; uint64_t start, remaining; uint64_t cluster_offset; uint64_t cur_bytes; int ret; trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset, *num); assert((offset & ~BDRV_SECTOR_MASK) == 0); again: start = offset; remaining = *num << BDRV_SECTOR_BITS; cluster_offset = 0; *host_offset = 0; cur_bytes = 0; *m = NULL; while (true) { if (!*host_offset) { *host_offset = start_of_cluster(s, cluster_offset); } assert(remaining >= cur_bytes); start += cur_bytes; remaining -= cur_bytes; cluster_offset += cur_bytes; if (remaining == 0) { break; } cur_bytes = remaining; /* * Now start gathering as many contiguous clusters as possible: * * 1. Check for overlaps with in-flight allocations * * a) Overlap not in the first cluster -> shorten this request and * let the caller handle the rest in its next loop iteration. * * b) Real overlaps of two requests. Yield and restart the search * for contiguous clusters (the situation could have changed * while we were sleeping) * * c) TODO: Request starts in the same cluster as the in-flight * allocation ends. Shorten the COW of the in-fight allocation, * set cluster_offset to write to the same cluster and set up * the right synchronisation between the in-flight request and * the new one. */ ret = handle_dependencies(bs, start, &cur_bytes, m); if (ret == -EAGAIN) { /* Currently handle_dependencies() doesn't yield if we already had * an allocation. If it did, we would have to clean up the L2Meta * structs before starting over. */ assert(*m == NULL); goto again; } else if (ret < 0) { return ret; } else if (cur_bytes == 0) { break; } else { /* handle_dependencies() may have decreased cur_bytes (shortened * the allocations below) so that the next dependency is processed * correctly during the next loop iteration. */ } /* * 2. Count contiguous COPIED clusters. */ ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m); if (ret < 0) { return ret; } else if (ret) { continue; } else if (cur_bytes == 0) { break; } /* * 3. If the request still hasn't completed, allocate new clusters, * considering any cluster_offset of steps 1c or 2. */ ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m); if (ret < 0) { return ret; } else if (ret) { continue; } else { assert(cur_bytes == 0); break; } } *num -= remaining >> BDRV_SECTOR_BITS; assert(*num > 0); assert(*host_offset != 0); return 0; } static int decompress_buffer(uint8_t *out_buf, int out_buf_size, const uint8_t *buf, int buf_size) { z_stream strm1, *strm = &strm1; int ret, out_len; memset(strm, 0, sizeof(*strm)); strm->next_in = (uint8_t *)buf; strm->avail_in = buf_size; strm->next_out = out_buf; strm->avail_out = out_buf_size; ret = inflateInit2(strm, -12); if (ret != Z_OK) return -1; ret = inflate(strm, Z_FINISH); out_len = strm->next_out - out_buf; if ((ret != Z_STREAM_END && ret != Z_BUF_ERROR) || out_len != out_buf_size) { inflateEnd(strm); return -1; } inflateEnd(strm); return 0; } int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset) { BDRVQcowState *s = bs->opaque; int ret, csize, nb_csectors, sector_offset; uint64_t coffset; coffset = cluster_offset & s->cluster_offset_mask; if (s->cluster_cache_offset != coffset) { nb_csectors = ((cluster_offset >> s->csize_shift) & s->csize_mask) + 1; sector_offset = coffset & 511; csize = nb_csectors * 512 - sector_offset; BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED); ret = bdrv_read(bs->file, coffset >> 9, s->cluster_data, nb_csectors); if (ret < 0) { return ret; } if (decompress_buffer(s->cluster_cache, s->cluster_size, s->cluster_data + sector_offset, csize) < 0) { return -EIO; } s->cluster_cache_offset = coffset; } return 0; } /* * This discards as many clusters of nb_clusters as possible at once (i.e. * all clusters in the same L2 table) and returns the number of discarded * clusters. */ static int discard_single_l2(BlockDriverState *bs, uint64_t offset, unsigned int nb_clusters, enum qcow2_discard_type type) { 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]); /* * Make sure that a discarded area reads back as zeroes for v3 images * (we cannot do it for v2 without actually writing a zero-filled * buffer). We can skip the operation if the cluster is already marked * as zero, or if it's unallocated and we don't have a backing file. * * TODO We might want to use bdrv_get_block_status(bs) here, but we're * holding s->lock, so that doesn't work today. */ if (old_offset & QCOW_OFLAG_ZERO) { continue; } if ((old_offset & L2E_OFFSET_MASK) == 0 && !bs->backing_hd) { continue; } /* First remove L2 entries */ qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); if (s->qcow_version >= 3) { l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); } else { l2_table[l2_index + i] = cpu_to_be64(0); } /* Then decrease the refcount */ qcow2_free_any_clusters(bs, old_offset, 1, type); } ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); if (ret < 0) { return ret; } return nb_clusters; } int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors, enum qcow2_discard_type type) { BDRVQcowState *s = bs->opaque; uint64_t end_offset; unsigned int nb_clusters; int ret; end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS); /* Round start up and end down */ offset = align_offset(offset, s->cluster_size); end_offset = start_of_cluster(s, end_offset); if (offset > end_offset) { return 0; } nb_clusters = size_to_clusters(s, end_offset - offset); s->cache_discards = true; /* Each L2 table is handled by its own loop iteration */ while (nb_clusters > 0) { ret = discard_single_l2(bs, offset, nb_clusters, type); if (ret < 0) { goto fail; } nb_clusters -= ret; offset += (ret * s->cluster_size); } ret = 0; fail: s->cache_discards = false; qcow2_process_discards(bs, ret); return ret; } /* * 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, QCOW2_DISCARD_REQUEST); } 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); s->cache_discards = true; while (nb_clusters > 0) { ret = zero_single_l2(bs, offset, nb_clusters); if (ret < 0) { goto fail; } nb_clusters -= ret; offset += (ret * s->cluster_size); } ret = 0; fail: s->cache_discards = false; qcow2_process_discards(bs, ret); return ret; } /* * Expands all zero clusters in a specific L1 table (or deallocates them, for * non-backed non-pre-allocated zero clusters). * * expanded_clusters is a bitmap where every bit corresponds to one cluster in * the image file; a bit gets set if the corresponding cluster has been used for * zero expansion (i.e., has been filled with zeroes and is referenced from an * L2 table). nb_clusters contains the total cluster count of the image file, * i.e., the number of bits in expanded_clusters. */ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table, int l1_size, uint8_t **expanded_clusters, uint64_t *nb_clusters) { BDRVQcowState *s = bs->opaque; bool is_active_l1 = (l1_table == s->l1_table); uint64_t *l2_table = NULL; int ret; int i, j; if (!is_active_l1) { /* inactive L2 tables require a buffer to be stored in when loading * them from disk */ l2_table = qemu_blockalign(bs, s->cluster_size); } for (i = 0; i < l1_size; i++) { uint64_t l2_offset = l1_table[i] & L1E_OFFSET_MASK; bool l2_dirty = false; if (!l2_offset) { /* unallocated */ continue; } if (is_active_l1) { /* get active L2 tables from cache */ ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset, (void **)&l2_table); } else { /* load inactive L2 tables from disk */ ret = bdrv_read(bs->file, l2_offset / BDRV_SECTOR_SIZE, (void *)l2_table, s->cluster_sectors); } if (ret < 0) { goto fail; } for (j = 0; j < s->l2_size; j++) { uint64_t l2_entry = be64_to_cpu(l2_table[j]); int64_t offset = l2_entry & L2E_OFFSET_MASK, cluster_index; int cluster_type = qcow2_get_cluster_type(l2_entry); bool preallocated = offset != 0; if (cluster_type == QCOW2_CLUSTER_NORMAL) { cluster_index = offset >> s->cluster_bits; assert((cluster_index >= 0) && (cluster_index < *nb_clusters)); if ((*expanded_clusters)[cluster_index / 8] & (1 << (cluster_index % 8))) { /* Probably a shared L2 table; this cluster was a zero * cluster which has been expanded, its refcount * therefore most likely requires an update. */ ret = qcow2_update_cluster_refcount(bs, cluster_index, 1, QCOW2_DISCARD_NEVER); if (ret < 0) { goto fail; } /* Since we just increased the refcount, the COPIED flag may * no longer be set. */ l2_table[j] = cpu_to_be64(l2_entry & ~QCOW_OFLAG_COPIED); l2_dirty = true; } continue; } else if (qcow2_get_cluster_type(l2_entry) != QCOW2_CLUSTER_ZERO) { continue; } if (!preallocated) { if (!bs->backing_hd) { /* not backed; therefore we can simply deallocate the * cluster */ l2_table[j] = 0; l2_dirty = true; continue; } offset = qcow2_alloc_clusters(bs, s->cluster_size); if (offset < 0) { ret = offset; goto fail; } } ret = qcow2_pre_write_overlap_check(bs, 0, offset, s->cluster_size); if (ret < 0) { if (!preallocated) { qcow2_free_clusters(bs, offset, s->cluster_size, QCOW2_DISCARD_ALWAYS); } goto fail; } ret = bdrv_write_zeroes(bs->file, offset / BDRV_SECTOR_SIZE, s->cluster_sectors, 0); if (ret < 0) { if (!preallocated) { qcow2_free_clusters(bs, offset, s->cluster_size, QCOW2_DISCARD_ALWAYS); } goto fail; } l2_table[j] = cpu_to_be64(offset | QCOW_OFLAG_COPIED); l2_dirty = true; cluster_index = offset >> s->cluster_bits; if (cluster_index >= *nb_clusters) { uint64_t old_bitmap_size = (*nb_clusters + 7) / 8; uint64_t new_bitmap_size; /* The offset may lie beyond the old end of the underlying image * file for growable files only */ assert(bs->file->growable); *nb_clusters = size_to_clusters(s, bs->file->total_sectors * BDRV_SECTOR_SIZE); new_bitmap_size = (*nb_clusters + 7) / 8; *expanded_clusters = g_realloc(*expanded_clusters, new_bitmap_size); /* clear the newly allocated space */ memset(&(*expanded_clusters)[old_bitmap_size], 0, new_bitmap_size - old_bitmap_size); } assert((cluster_index >= 0) && (cluster_index < *nb_clusters)); (*expanded_clusters)[cluster_index / 8] |= 1 << (cluster_index % 8); } if (is_active_l1) { if (l2_dirty) { qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); qcow2_cache_depends_on_flush(s->l2_table_cache); } ret = qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table); if (ret < 0) { l2_table = NULL; goto fail; } } else { if (l2_dirty) { ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_INACTIVE_L2 | QCOW2_OL_ACTIVE_L2, l2_offset, s->cluster_size); if (ret < 0) { goto fail; } ret = bdrv_write(bs->file, l2_offset / BDRV_SECTOR_SIZE, (void *)l2_table, s->cluster_sectors); if (ret < 0) { goto fail; } } } } ret = 0; fail: if (l2_table) { if (!is_active_l1) { qemu_vfree(l2_table); } else { if (ret < 0) { qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table); } else { ret = qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table); } } } return ret; } /* * For backed images, expands all zero clusters on the image. For non-backed * images, deallocates all non-pre-allocated zero clusters (and claims the * allocation for pre-allocated ones). This is important for downgrading to a * qcow2 version which doesn't yet support metadata zero clusters. */ int qcow2_expand_zero_clusters(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; uint64_t *l1_table = NULL; uint64_t nb_clusters; uint8_t *expanded_clusters; int ret; int i, j; nb_clusters = size_to_clusters(s, bs->file->total_sectors * BDRV_SECTOR_SIZE); expanded_clusters = g_malloc0((nb_clusters + 7) / 8); ret = expand_zero_clusters_in_l1(bs, s->l1_table, s->l1_size, &expanded_clusters, &nb_clusters); if (ret < 0) { goto fail; } /* Inactive L1 tables may point to active L2 tables - therefore it is * necessary to flush the L2 table cache before trying to access the L2 * tables pointed to by inactive L1 entries (else we might try to expand * zero clusters that have already been expanded); furthermore, it is also * necessary to empty the L2 table cache, since it may contain tables which * are now going to be modified directly on disk, bypassing the cache. * qcow2_cache_empty() does both for us. */ ret = qcow2_cache_empty(bs, s->l2_table_cache); if (ret < 0) { goto fail; } for (i = 0; i < s->nb_snapshots; i++) { int l1_sectors = (s->snapshots[i].l1_size * sizeof(uint64_t) + BDRV_SECTOR_SIZE - 1) / BDRV_SECTOR_SIZE; l1_table = g_realloc(l1_table, l1_sectors * BDRV_SECTOR_SIZE); ret = bdrv_read(bs->file, s->snapshots[i].l1_table_offset / BDRV_SECTOR_SIZE, (void *)l1_table, l1_sectors); if (ret < 0) { goto fail; } for (j = 0; j < s->snapshots[i].l1_size; j++) { be64_to_cpus(&l1_table[j]); } ret = expand_zero_clusters_in_l1(bs, l1_table, s->snapshots[i].l1_size, &expanded_clusters, &nb_clusters); if (ret < 0) { goto fail; } } ret = 0; fail: g_free(expanded_clusters); g_free(l1_table); return ret; }