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authorEric Blake <eblake@redhat.com>2017-04-06 20:37:09 -0500
committerMax Reitz <mreitz@redhat.com>2017-04-28 16:02:03 +0200
commit048c5fd1bfc787adcb1b726ce997e87fe44545fd (patch)
treefad9a99219396240b4a7612ddd2ee38ff3a60b42 /block
parentf59adb325618a2d2ba16aece551e7ab6acadb0ae (diff)
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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>
Diffstat (limited to 'block')
-rw-r--r--block/qcow2.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index 4ca4cf0..5c1573c 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -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);