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block: fix alignment calculations in bdrv_co_do_zero_pwritev

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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>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Denis V. Lunev 2017-04-26 11:40:46 +03:00 committed by Kevin Wolf
parent de234897b6
commit f13ce1be35
1 changed files with 1 additions and 1 deletions
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block/io.c
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@ -1444,7 +1444,7 @@ 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);