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[PATCH 1/2] block/io: Update BSC only if want_zero is true
From: |
Hanna Reitz |
Subject: |
[PATCH 1/2] block/io: Update BSC only if want_zero is true |
Date: |
Mon, 17 Jan 2022 17:26:48 +0100 |
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 <nsoffer@redhat.com>
Fixes: 0bc329fbb009f8601cec23bf2bc48ead0c5a5fa2
("block: block-status cache for data regions")
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
block/io.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/block/io.c b/block/io.c
index bb0a254def..4e4cb556c5 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))
{
/*
--
2.33.1