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block: bdrv_set_backing_hd(): use drained section 

Graph modifications should be done in drained section. stream_prepare()
handler of block stream job call bdrv_set_backing_hd() without using
drained section and it's theoretically possible that some IO request
will interleave with graph modification and will use outdated pointers
to removed block nodes.

Some other callers use bdrv_set_backing_hd() not caring about drained
sections too. So it seems good to make a drained section exactly in
bdrv_set_backing_hd().

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20220124173741.2984056-1-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2022-01-24 18:37:41 +01:00 committed by Kevin Wolf
parent e66e665f15
commit c0829cb1fd
1 changed files with 4 additions and 0 deletions
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4
block.c
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@ -3341,6 +3341,8 @@ int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
int ret;
Transaction *tran = tran_new();
bdrv_drained_begin(bs);
ret = bdrv_set_backing_noperm(bs, backing_hd, tran, errp);
if (ret < 0) {
goto out;
@ -3350,6 +3352,8 @@ int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
out:
tran_finalize(tran, ret);
bdrv_drained_end(bs);
return ret;
}