diff options
Diffstat (limited to 'block/qcow2-cluster.c')
| -rw-r--r-- | block/qcow2-cluster.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index c57f39dd2b..36c1bed350 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1367,13 +1367,31 @@ static int discard_single_l2(BlockDriverState *bs, uint64_t offset, uint64_t old_offset; old_offset = be64_to_cpu(l2_table[l2_index + i]); - if ((old_offset & L2E_OFFSET_MASK) == 0) { + + /* + * 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); - l2_table[l2_index + i] = cpu_to_be64(0); + 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); |