haraldwolff/qemu-patch-raspberry4
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block: Fix copy-on-read crash with partial final cluster

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If the virtual disk size isn't aligned to full clusters,
bdrv_co_do_copy_on_readv() may get pnum == 0 before having the full
cluster completed, which will let it run into an assertion failure:

qemu-io: block/io.c:1203: bdrv_co_do_copy_on_readv: Assertion `skip_bytes < pnum' failed.

Check for EOF, assert that we read at least as much as the read request
originally wanted to have (which is true at EOF because otherwise
bdrv_check_byte_request() would already have returned an error) and
return success early even though we couldn't copy the full cluster.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2018-07-06 18:41:07 +02:00
parent b994c5bc51
commit b0ddcbbb36
3 changed files with 23 additions and 0 deletions
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6
block/io.c
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@ -1200,6 +1200,12 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
pnum = MIN(cluster_bytes, max_transfer);
}
/* Stop at EOF if the image ends in the middle of the cluster */
if (ret == 0 && pnum == 0) {
assert(progress >= bytes);
break;
}
assert(skip_bytes < pnum);
if (ret <= 0) {

9
tests/qemu-iotests/197
View file

@ -109,6 +109,15 @@ $QEMU_IO -f qcow2 -c map "$TEST_WRAP"
_check_test_img
$QEMU_IMG compare -f $IMGFMT -F qcow2 "$TEST_IMG" "$TEST_WRAP"
echo
echo '=== Partial final cluster ==='
echo
_make_test_img 1024
$QEMU_IO -f $IMGFMT -C -c 'read 0 1024' "$TEST_IMG" | _filter_qemu_io
$QEMU_IO -f $IMGFMT -c map "$TEST_IMG"
_check_test_img
# success, all done
echo '*** done'
status=0

8
tests/qemu-iotests/197.out
View file

@ -23,4 +23,12 @@ can't open device TEST_DIR/t.wrap.qcow2: Can't use copy-on-read on read-only dev
1023.938 MiB (0x3fff0000) bytes not allocated at offset 3 GiB (0xc0010000)
No errors were found on the image.
Images are identical.
=== Partial final cluster ===
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1024
read 1024/1024 bytes at offset 0
1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
1 KiB (0x400) bytes allocated at offset 0 bytes (0x0)
No errors were found on the image.
*** done