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author | Max Reitz <mreitz@redhat.com> | 2013-09-03 10:09:52 +0200 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2013-09-12 10:12:46 +0200 |
commit | 32b6444d23d0ff618d73e5b766600cd258066169 (patch) | |
tree | 423a268eaa2281d71e0d7d1d75ade22e153510aa | |
parent | e7108feaace8e02b3a4bf010448fc2744f753381 (diff) | |
download | qemu-32b6444d23d0ff618d73e5b766600cd258066169.zip qemu-32b6444d23d0ff618d73e5b766600cd258066169.tar.gz qemu-32b6444d23d0ff618d73e5b766600cd258066169.tar.bz2 |
qcow2-cluster: Expand zero clusters
Add functionality for expanding zero clusters. This is necessary for
downgrading the image version to one without zero cluster support.
For non-backed images, this function may also just discard zero clusters
instead of truly expanding them.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r-- | block/qcow2-cluster.c | 233 | ||||
-rw-r--r-- | block/qcow2-refcount.c | 29 | ||||
-rw-r--r-- | block/qcow2.h | 5 |
3 files changed, 253 insertions, 14 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index b0d688e..738ff73 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1497,3 +1497,236 @@ fail: 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); + + 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 (!offset) { + /* not 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, QCOW2_OL_DEFAULT, + offset, s->cluster_size); + if (ret < 0) { + 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); + if (ret < 0) { + 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; + 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_DEFAULT & + ~(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; + int cluster_to_sector_bits = s->cluster_bits - BDRV_SECTOR_BITS; + uint64_t nb_clusters; + uint8_t *expanded_clusters; + int ret; + int i, j; + + nb_clusters = (bs->total_sectors + (1 << cluster_to_sector_bits) - 1) + >> cluster_to_sector_bits; + 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; +} diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index ba129de..4264148 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -601,10 +601,10 @@ fail: * If the return value is non-negative, it is the new refcount of the cluster. * If it is negative, it is -errno and indicates an error. */ -static int update_cluster_refcount(BlockDriverState *bs, - int64_t cluster_index, - int addend, - enum qcow2_discard_type type) +int qcow2_update_cluster_refcount(BlockDriverState *bs, + int64_t cluster_index, + int addend, + enum qcow2_discard_type type) { BDRVQcowState *s = bs->opaque; int ret; @@ -733,8 +733,8 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) if (free_in_cluster == 0) s->free_byte_offset = 0; if ((offset & (s->cluster_size - 1)) != 0) - update_cluster_refcount(bs, offset >> s->cluster_bits, 1, - QCOW2_DISCARD_NEVER); + qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1, + QCOW2_DISCARD_NEVER); } else { offset = qcow2_alloc_clusters(bs, s->cluster_size); if (offset < 0) { @@ -744,8 +744,8 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) if ((cluster_offset + s->cluster_size) == offset) { /* we are lucky: contiguous data */ offset = s->free_byte_offset; - update_cluster_refcount(bs, offset >> s->cluster_bits, 1, - QCOW2_DISCARD_NEVER); + qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1, + QCOW2_DISCARD_NEVER); s->free_byte_offset += size; } else { s->free_byte_offset = offset; @@ -754,8 +754,8 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) } /* The cluster refcount was incremented, either by qcow2_alloc_clusters() - * or explicitly by update_cluster_refcount(). Refcount blocks must be - * flushed before the caller's L2 table updates. + * or explicitly by qcow2_update_cluster_refcount(). Refcount blocks must + * be flushed before the caller's L2 table updates. */ qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache); return offset; @@ -896,8 +896,9 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, break; } if (addend != 0) { - refcount = update_cluster_refcount(bs, cluster_index, addend, - QCOW2_DISCARD_SNAPSHOT); + refcount = qcow2_update_cluster_refcount(bs, + cluster_index, addend, + QCOW2_DISCARD_SNAPSHOT); } else { refcount = get_refcount(bs, cluster_index); } @@ -936,8 +937,8 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, if (addend != 0) { - refcount = update_cluster_refcount(bs, l2_offset >> s->cluster_bits, addend, - QCOW2_DISCARD_SNAPSHOT); + refcount = qcow2_update_cluster_refcount(bs, l2_offset >> + s->cluster_bits, addend, QCOW2_DISCARD_SNAPSHOT); } else { refcount = get_refcount(bs, l2_offset >> s->cluster_bits); } diff --git a/block/qcow2.h b/block/qcow2.h index 35c822b..48080fd 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -411,6 +411,9 @@ int qcow2_update_header(BlockDriverState *bs); int qcow2_refcount_init(BlockDriverState *bs); void qcow2_refcount_close(BlockDriverState *bs); +int qcow2_update_cluster_refcount(BlockDriverState *bs, int64_t cluster_index, + int addend, enum qcow2_discard_type type); + int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size); int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, int nb_clusters); @@ -458,6 +461,8 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors, enum qcow2_discard_type type); int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors); +int qcow2_expand_zero_clusters(BlockDriverState *bs); + /* qcow2-snapshot.c functions */ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info); int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id); |