| From e67b77c791ca2778198c9e7088f3266ed2da7a55 Mon Sep 17 00:00:00 2001 |
| From: Jeff Moyer <jmoyer@redhat.com> |
| Date: Mon, 17 Oct 2011 12:57:23 +0200 |
| Subject: blk-flush: move the queue kick into |
| |
| From: Jeff Moyer <jmoyer@redhat.com> |
| |
| commit e67b77c791ca2778198c9e7088f3266ed2da7a55 upstream. |
| |
| A dm-multipath user reported[1] a problem when trying to boot |
| a kernel with commit 4853abaae7e4a2af938115ce9071ef8684fb7af4 |
| (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> |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| block/blk-core.c | 2 ++ |
| block/blk-flush.c | 1 - |
| 2 files changed, 2 insertions(+), 1 deletion(-) |
| |
| --- a/block/blk-core.c |
| +++ b/block/blk-core.c |
| @@ -1725,6 +1725,8 @@ int blk_insert_cloned_request(struct req |
| 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; |
| --- 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; |
| } |
| |