diff options
| -rw-r--r-- | block.c | 14 | ||||
| -rw-r--r-- | block/qcow2-cluster.c | 72 | ||||
| -rw-r--r-- | block/qcow2.c | 21 | ||||
| -rw-r--r-- | block/qcow2.h | 1 |
4 files changed, 105 insertions, 3 deletions
@@ -80,6 +80,8 @@ static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs, void *opaque, bool is_write); static void coroutine_fn bdrv_co_do_rw(void *opaque); +static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, + int64_t sector_num, int nb_sectors); static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors, bool is_write, double elapsed_time, uint64_t *wait); @@ -1708,8 +1710,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs, if (drv->bdrv_co_write_zeroes && buffer_is_zero(bounce_buffer, iov.iov_len)) { - ret = drv->bdrv_co_write_zeroes(bs, cluster_sector_num, - cluster_nb_sectors); + ret = bdrv_co_do_write_zeroes(bs, cluster_sector_num, + cluster_nb_sectors); } else { ret = drv->bdrv_co_writev(bs, cluster_sector_num, cluster_nb_sectors, &bounce_qiov); @@ -1819,9 +1821,15 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, struct iovec iov; int ret; + /* TODO Emulate only part of misaligned requests instead of letting block + * drivers return -ENOTSUP and emulate everything */ + /* First try the efficient write zeroes operation */ if (drv->bdrv_co_write_zeroes) { - return drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors); + ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors); + if (ret != -ENOTSUP) { + return ret; + } } /* Fall back to bounce buffer if write zeroes is unsupported */ diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 5e5f5cf9ad..a747a88e13 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1102,3 +1102,75 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset, return 0; } + +/* + * 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); + } 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); + + while (nb_clusters > 0) { + ret = zero_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 41b195d91b..ad46c03c2f 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1281,6 +1281,26 @@ static int qcow2_make_empty(BlockDriverState *bs) return 0; } +static coroutine_fn int qcow2_co_write_zeroes(BlockDriverState *bs, + int64_t sector_num, int nb_sectors) +{ + int ret; + BDRVQcowState *s = bs->opaque; + + /* Emulate misaligned zero writes */ + if (sector_num % s->cluster_sectors || nb_sectors % s->cluster_sectors) { + return -ENOTSUP; + } + + /* Whatever is left can use real zero clusters */ + qemu_co_mutex_lock(&s->lock); + ret = qcow2_zero_clusters(bs, sector_num << BDRV_SECTOR_BITS, + nb_sectors); + qemu_co_mutex_unlock(&s->lock); + + return ret; +} + static coroutine_fn int qcow2_co_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors) { @@ -1558,6 +1578,7 @@ static BlockDriver bdrv_qcow2 = { .bdrv_co_writev = qcow2_co_writev, .bdrv_co_flush_to_os = qcow2_co_flush_to_os, + .bdrv_co_write_zeroes = qcow2_co_write_zeroes, .bdrv_co_discard = qcow2_co_discard, .bdrv_truncate = qcow2_truncate, .bdrv_write_compressed = qcow2_write_compressed, diff --git a/block/qcow2.h b/block/qcow2.h index 2a982445a1..93567f6451 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -283,6 +283,7 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m); int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors); +int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors); /* qcow2-snapshot.c functions */ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info); |