diff mbox

[4/5] qcow2: fix condition in is_zero_cluster

Message ID 1463476543-3087-5-git-send-email-den@openvz.org (mailing list archive)
State New, archived
Headers show

Commit Message

Denis V. Lunev May 17, 2016, 9:15 a.m. UTC 
We should check for (res & BDRV_BLOCK_ZERO) only. The situation when we
will have !(res & BDRV_BLOCK_DATA) and will not have BDRV_BLOCK_ZERO is
not possible.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Kevin Wolf May 17, 2016, 3:11 p.m. UTC | #1 
Am 17.05.2016 um 11:15 hat Denis V. Lunev geschrieben:
> We should check for (res & BDRV_BLOCK_ZERO) only. The situation when we
> will have !(res & BDRV_BLOCK_DATA) and will not have BDRV_BLOCK_ZERO is
> not possible.

The patch is okay, but I'm correcting this paragraph into:

    We should check for (res & BDRV_BLOCK_ZERO) only. The situation when we
    will have !(res & BDRV_BLOCK_DATA) and will not have BDRV_BLOCK_ZERO is
    not possible for images with bdi.unallocated_blocks_are_zero == true.

    For those images where it's false, however, it can happen and we must
    not consider the data zeroed then or we would corrupt the image.

Kevin
diff mbox

Patch

diff --git a/block/qcow2.c b/block/qcow2.c
index 97bf870..05beb64 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2412,7 +2412,7 @@  static bool is_zero_cluster(BlockDriverState *bs, int64_t start)
     BlockDriverState *file;
     int64_t res = bdrv_get_block_status_above(bs, NULL, start,
                                               s->cluster_sectors, &nr, &file);
-    return res >= 0 && ((res & BDRV_BLOCK_ZERO) || !(res & BDRV_BLOCK_DATA));
+    return res >= 0 && (res & BDRV_BLOCK_ZERO);
 }
 
 static bool is_zero_cluster_top_locked(BlockDriverState *bs, int64_t start)