From 000a39225ba4dee2a836842076b428de522f0966 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 14 Feb 2012 11:14:01 +0100 Subject: [PATCH 36/99] qcow2: Add bdrv_discard support RH-Author: Kevin Wolf Message-id: <1329218101-24213-37-git-send-email-kwolf@redhat.com> Patchwork-id: 37227 O-Subject: [RHEL-6.3 qemu-kvm PATCH v2 36/96] qcow2: Add bdrv_discard support Bugzilla: 783950 RH-Acked-by: Paolo Bonzini RH-Acked-by: Marcelo Tosatti RH-Acked-by: Laszlo Ersek Bugzilla: 783950 This adds a bdrv_discard function to qcow2 that frees the discarded clusters. It does not yet pass the discard on to the underlying file system driver, but the space can be reused by future writes to the image. Signed-off-by: Kevin Wolf Reviewed-by: Stefan Hajnoczi (cherry picked from commit 5ea929e3d13622e5d06ca8795819f1590644cda2) Conflicts: block/qcow2.c Signed-off-by: Kevin Wolf --- block/qcow2-cluster.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++ block/qcow2.c | 8 +++++ block/qcow2.h | 2 + 3 files changed, 92 insertions(+), 0 deletions(-) Signed-off-by: Michal Novotny --- block/qcow2-cluster.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++ block/qcow2.c | 8 +++++ block/qcow2.h | 2 + 3 files changed, 92 insertions(+), 0 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 945bad4..85dd758 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -884,3 +884,85 @@ 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 ef1dd5e..46f7e59 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1272,6 +1272,13 @@ 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); +} + /* XXX: put compressed sectors first, then all the cluster aligned tables to avoid losing bytes in alignment */ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num, @@ -1501,6 +1508,7 @@ 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 9a6a025..8dc8d7d 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -212,6 +212,8 @@ 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); -- 1.7.7.5