Commit e67b77c7 authored Oct 17, 2011 by Jeff Moyer Committed by Jens Axboe Oct 24, 2011

blk-flush: move the queue kick into

A dm-multipath user reported[1] a problem when trying to boot
a kernel with commit 4853abaa
(block: fix flush machinery for stacking drivers with differring
flush flags) applied.  It turns out that an empty flush request
can be sent into blk_insert_flush.  When the BUG_ON was fixed
to allow for this, I/O on the underlying device would stall.  The
reason is that blk_insert_cloned_request does not kick the queue.
In the aforementioned commit, I had added a special case to
kick the queue if data was sent down but the queue flags did
not require a flush.  A better solution is to push the queue
kick up into blk_insert_cloned_request.

This patch, along with a follow-on which fixes the BUG_ON, fixes
the issue reported.

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

Stable note: 3.1
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 834f9f61

block/blk-core.c

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1725,6 +1725,8 @@ int blk_insert_cloned_request(struct request_queue q, struct request rq)
	where = ELEVATOR_INSERT_FLUSH;		where = ELEVATOR_INSERT_FLUSH;

	add_acct_request(q, rq, where);		add_acct_request(q, rq, where);
			if (where == ELEVATOR_INSERT_FLUSH)
			__blk_run_queue(q);
	spin_unlock_irqrestore(q->queue_lock, flags);		spin_unlock_irqrestore(q->queue_lock, flags);

	return 0;		return 0;

block/blk-flush.c

+0 −1

Original line number	Original line	Diff line number	Diff line
	@@ -330,7 +330,6 @@ void blk_insert_flush(struct request *rq)
	if ((policy & REQ_FSEQ_DATA) &&		if ((policy & REQ_FSEQ_DATA) &&
	!(policy & (REQ_FSEQ_PREFLUSH \| REQ_FSEQ_POSTFLUSH))) {		!(policy & (REQ_FSEQ_PREFLUSH \| REQ_FSEQ_POSTFLUSH))) {
	list_add_tail(&rq->queuelist, &q->queue_head);		list_add_tail(&rq->queuelist, &q->queue_head);
	blk_run_queue_async(q);
	return;		return;
	}		}