openkylin
/
qemu
mirror of https://gitee.com/openkylin/qemu.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

qcow2: Allow discard of final unaligned cluster 

As mentioned in commit 0c1bd46, we ignored requests to
discard the trailing cluster of an unaligned image.  While
discard is an advisory operation from the guest standpoint,
(and we are therefore free to ignore any request), our
qcow2 implementation exploits the fact that a discarded
cluster reads back as 0.  As long as we discard on cluster
boundaries, we are fine; but that means we could observe
non-zero data leaked at the tail of an unaligned image.

Enhance iotest 66 to cover this case, and fix the implementation
to honor a discard request on the final partial cluster.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-id: 20170407013709.18440-1-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Eric Blake 2017-04-06 20:37:09 -05:00 committed by Max Reitz
parent f59adb3256
commit 048c5fd1bf
3 changed files with 21 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
block/qcow2.c
View File

@ -2515,7 +2515,12 @@ static coroutine_fn int qcow2_co_pdiscard(BlockDriverState *bs,
if (!QEMU_IS_ALIGNED(offset | count, s->cluster_size)) {
assert(count < s->cluster_size);
return -ENOTSUP;
/* Ignore partial clusters, except for the special case of the
* complete partial cluster at the end of an unaligned file */
if (!QEMU_IS_ALIGNED(offset, s->cluster_size) ||
offset + count != bs->total_sectors * BDRV_SECTOR_SIZE) {
return -ENOTSUP;
}
}
qemu_co_mutex_lock(&s->lock);

12
tests/qemu-iotests/066
View File

@ -42,16 +42,18 @@ _supported_fmt qcow2
_supported_proto generic
_supported_os Linux
# Intentionally create an unaligned image
IMGOPTS="compat=1.1"
IMG_SIZE=64M
IMG_SIZE=$((64 * 1024 * 1024 + 512))
echo
echo "=== Testing snapshotting an image with zero clusters ==="
echo "=== Testing cluster discards ==="
echo
_make_test_img $IMG_SIZE
# Write some normal clusters, zero them (creating preallocated zero clusters)
# and discard those
$QEMU_IO -c "write 0 256k" -c "write -z 0 256k" -c "discard 0 256k" "$TEST_IMG" \
# Write some normal clusters, zero some of them (creating preallocated
# zero clusters) and discard everything. Everything should now read as 0.
$QEMU_IO -c "write 0 256k" -c "write -z 0 256k" -c "write 64M 512" \
-c "discard 0 $IMG_SIZE" -c "read -P 0 0 $IMG_SIZE" "$TEST_IMG" \
| _filter_qemu_io
# Check the image (there shouldn't be any leaks)
_check_test_img

12
tests/qemu-iotests/066.out
View File

@ -1,13 +1,17 @@
QA output created by 066
=== Testing snapshotting an image with zero clusters ===
=== Testing cluster discards ===
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67109376
wrote 262144/262144 bytes at offset 0
256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
wrote 262144/262144 bytes at offset 0
256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
discard 262144/262144 bytes at offset 0
256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
wrote 512/512 bytes at offset 67108864
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
discard 67109376/67109376 bytes at offset 0
64 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 67109376/67109376 bytes at offset 0
64 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
No errors were found on the image.
*** done