[1/1] block: fix alignment calculations in bdrv_co_do_zero_pwritev
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Message ID 1493196046-5607-1-git-send-email-den@openvz.org
State New
Headers show

Commit Message

Denis V. Lunev April 26, 2017, 8:40 a.m. UTC
tail_padding_bytes is calculated wrong. F.e. for
    offset = 0
    bytes = 2048
    align = 512
we will have tail_padding_bytes = 512 which is definitely wrong. The patch
fixes that arithmetics.

Fortunately this problem is harmless, we will have 1 extra allocation and
free thus there is no need to put this into stable. The problem is here
from the very beginning.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Fam Zheng <famz@redhat.com>
---
 block/io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Eric Blake April 26, 2017, 1:21 p.m. UTC | #1
On 04/26/2017 03:40 AM, Denis V. Lunev wrote:
> tail_padding_bytes is calculated wrong. F.e. for
>     offset = 0
>     bytes = 2048
>     align = 512
> we will have tail_padding_bytes = 512 which is definitely wrong. The patch
> fixes that arithmetics.
> 
> Fortunately this problem is harmless, we will have 1 extra allocation and
> free thus there is no need to put this into stable. The problem is here
> from the very beginning.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Fam Zheng <famz@redhat.com>
> ---
>  block/io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>
Kevin Wolf April 27, 2017, 2:44 p.m. UTC | #2
Am 26.04.2017 um 10:40 hat Denis V. Lunev geschrieben:
> tail_padding_bytes is calculated wrong. F.e. for
>     offset = 0
>     bytes = 2048
>     align = 512
> we will have tail_padding_bytes = 512 which is definitely wrong. The patch
> fixes that arithmetics.
> 
> Fortunately this problem is harmless, we will have 1 extra allocation and
> free thus there is no need to put this into stable. The problem is here
> from the very beginning.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Fam Zheng <famz@redhat.com>

Thanks, applied to block-next.

Kevin

Patch
diff mbox

diff --git a/block/io.c b/block/io.c
index a7142e0..1e1523b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1452,7 +1452,7 @@  static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
     int ret = 0;
 
     head_padding_bytes = offset & (align - 1);
-    tail_padding_bytes = align - ((offset + bytes) & (align - 1));
+    tail_padding_bytes = (align - (offset + bytes)) & (align - 1);
 
 
     assert(flags & BDRV_REQ_ZERO_WRITE);