diff options
| -rw-r--r-- | block/qcow2-cluster.c | 22 | ||||
| -rwxr-xr-x | tests/qemu-iotests/046 | 18 |
2 files changed, 34 insertions, 6 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); diff --git a/tests/qemu-iotests/046 b/tests/qemu-iotests/046 index 2d44bbb187..e0be46cf2b 100755 --- a/tests/qemu-iotests/046 +++ b/tests/qemu-iotests/046 @@ -193,6 +193,16 @@ echo "== Verify image content ==" function verify_io() { + if ($QEMU_IMG info -f "$IMGFMT" "$TEST_IMG" | grep "compat: 0.10" > /dev/null); then + # For v2 images, discarded clusters are read from the backing file + # Keep the variable empty so that the backing file value can be used as + # the default below + discarded= + else + # Discarded clusters are zeroed for v3 or later + discarded=0 + fi + echo read -P 0 0 0x10000 echo read -P 1 0x10000 0x2000 @@ -221,16 +231,16 @@ function verify_io() echo read -P 70 0x78000 0x6000 echo read -P 7 0x7e000 0x2000 - echo read -P 8 0x80000 0x6000 + echo read -P ${discarded:-8} 0x80000 0x6000 echo read -P 80 0x86000 0x2000 - echo read -P 8 0x88000 0x2000 + echo read -P ${discarded:-8} 0x88000 0x2000 echo read -P 81 0x8a000 0xe000 echo read -P 90 0x98000 0x6000 echo read -P 9 0x9e000 0x2000 - echo read -P 10 0xa0000 0x6000 + echo read -P ${discarded:-10} 0xa0000 0x6000 echo read -P 100 0xa6000 0x2000 - echo read -P 10 0xa8000 0x2000 + echo read -P ${discarded:-10} 0xa8000 0x2000 echo read -P 101 0xaa000 0xe000 echo read -P 110 0xb8000 0x8000 |