blk-flush: move the queue kick into

A dm-multipath user reported[1] a problem when trying to boot a kernel with commit 4853aba (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 <[email protected]> Signed-off-by: Jeff Moyer <[email protected]> Acked-by: Tejun Heo <[email protected]> Stable note: 3.1 Cc: [email protected] Signed-off-by: Jens Axboe <[email protected]>
kishon · Oct 24, 2011 · e67b77c · e67b77c
1 parent 834f9f6
commit e67b77c
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diff --git a/block/blk-core.c b/block/blk-core.c
@@ -1725,6 +1725,8 @@ int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
 		where = ELEVATOR_INSERT_FLUSH;
 
 	add_acct_request(q, rq, where);
+	if (where == ELEVATOR_INSERT_FLUSH)
+		__blk_run_queue(q);
 	spin_unlock_irqrestore(q->queue_lock, flags);
 
 	return 0;

diff --git a/block/blk-flush.c b/block/blk-flush.c
@@ -330,7 +330,6 @@ void blk_insert_flush(struct request *rq)
 	if ((policy & REQ_FSEQ_DATA) &&
 	    !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
 		list_add_tail(&rq->queuelist, &q->queue_head);
-		blk_run_queue_async(q);
 		return;
 	}