From: Hanna Reitz <hre...@redhat.com>
We update the block-status cache whenever we get new information from a
bdrv_co_block_status() call to the block driver. However, if we have
passed want_zero=false to that call, it may flag areas containing zeroes
as data, and so we would update the block-status cache with wrong
information.
Therefore, we should not update the cache with want_zero=false.
Reported-by: Nir Soffer <nsof...@redhat.com>
Fixes: 0bc329fbb00 ("block: block-status cache for data regions")
Reviewed-by: Nir Soffer <nsof...@redhat.com>
Cc: qemu-sta...@nongnu.org
Signed-off-by: Hanna Reitz <hre...@redhat.com>
Message-Id: <20220118170000.49423-2-hre...@redhat.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
block/io.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/block/io.c b/block/io.c
index bb0a254def11..4e4cb556c586 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2497,8 +2497,12 @@ static int coroutine_fn
bdrv_co_block_status(BlockDriverState *bs,
* non-protocol nodes, and then it is never used. However, filling
* the cache requires an RCU update, so double check here to avoid
* such an update if possible.
+ *
+ * Check want_zero, because we only want to update the cache when
we
+ * have accurate information about what is zero and what is data.
*/
- if (ret == (BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID) &&
+ if (want_zero &&
+ ret == (BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID) &&
QLIST_EMPTY(&bs->children))
{
/*
--
2.34.1
