diff options
| -rw-r--r-- | block/qcow2-cluster.c | 82 | ||||
| -rw-r--r-- | block/qcow2.c | 8 | ||||
| -rw-r--r-- | block/qcow2.h | 2 |
3 files changed, 92 insertions, 0 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 1c2003a..5fb8c66 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -888,3 +888,85 @@ int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset) } 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) +{ + BDRVQcowState *s = bs->opaque; + uint64_t l2_offset, *l2_table; + int l2_index; + int ret; + int i; + + ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &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]); + old_offset &= ~QCOW_OFLAG_COPIED; + + if (old_offset == 0) { + continue; + } + + /* First remove L2 entries */ + qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); + l2_table[l2_index + i] = cpu_to_be64(0); + + /* Then decrease the refcount */ + qcow2_free_any_clusters(bs, old_offset, 1); + } + + 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) +{ + 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 &= ~(s->cluster_size - 1); + + if (offset > end_offset) { + return 0; + } + + nb_clusters = size_to_clusters(s, end_offset - offset); + + /* Each L2 table is handled by its own loop iteration */ + while (nb_clusters > 0) { + ret = discard_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.c b/block/qcow2.c index 49bf7b9..dbe4fdd 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1084,6 +1084,13 @@ static int qcow2_make_empty(BlockDriverState *bs) return 0; } +static int qcow2_discard(BlockDriverState *bs, int64_t sector_num, + int nb_sectors) +{ + return qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS, + nb_sectors); +} + static int qcow2_truncate(BlockDriverState *bs, int64_t offset) { BDRVQcowState *s = bs->opaque; @@ -1349,6 +1356,7 @@ static BlockDriver bdrv_qcow2 = { .bdrv_aio_writev = qcow2_aio_writev, .bdrv_aio_flush = qcow2_aio_flush, + .bdrv_discard = qcow2_discard, .bdrv_truncate = qcow2_truncate, .bdrv_write_compressed = qcow2_write_compressed, diff --git a/block/qcow2.h b/block/qcow2.h index 6d80120..a019831 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -209,6 +209,8 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, int compressed_size); int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m); +int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset, + int nb_sectors); /* qcow2-snapshot.c functions */ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info); |