A user reported a regression due to commit
4853abaae7e4a2af938115ce9071ef8684fb7af4 (block: fix flush
machinery for stacking drivers with differring flush flags).
Part of the problem is that blk_insert_flush required a
single bio be attached to the request. In reality, having
no attached bio is also a valid case, as can be observed with
an empty flush.

[1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.html

Reported-by: Christophe Saout <christophe@saout.de>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
---
block/blk-flush.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 0ff29c6..720ad60 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -320,7 +320,7 @@ void blk_insert_flush(struct request *rq)
return;
}

- BUG_ON(!rq->bio || rq->bio != rq->biotail);
+ BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */

/*
* If there's data but flush is not necessary, the request can be
--
1.7.1

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On Wed, Oct 12, 2011 at 05:22:42PM -0400, Jeff Moyer wrote:
> A user reported a regression due to commit
> 4853abaae7e4a2af938115ce9071ef8684fb7af4 (block: fix flush
> machinery for stacking drivers with differring flush flags).
> Part of the problem is that blk_insert_flush required a
> single bio be attached to the request. In reality, having
> no attached bio is also a valid case, as can be observed with
> an empty flush.
>
> [1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.html
>
> Reported-by: Christophe Saout <christophe@saout.de>
> Signed-off-by: Jeff Moyer <jmoyer@redhat.com
> Signed-off-by: Jeff Moyer <jmoyer@redhat.com>

Duplicate SOB's and missing space after '/*' in the comment. Other
than that,

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

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tejun

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