From 908991f13837d34a445fc313e44fd7b6dbb5c5c9 Mon Sep 17 00:00:00 2001 From: Linas Vepstas Date: Sat, 21 Apr 2007 00:13:30 +0200 Subject: [PATCH] elevator: move clearing of unplug flag earlier A flag was recently added to the elevator code to avoid performing an unplug when reuests are being re-queued. The goal of this flag was to avoid a deep recursion that can occur when re-queueing requests after a SCSI device/host reset. See http://lkml.org/lkml/2006/5/17/254 However, that fix added the flag near the bottom of a case statement, where an earlier break (in an if statement) could transport one out of the case, without setting the flag. This patch sets the flag earlier in the case statement. I re-discovered the deep recursion recently during testing; I was told that it was a known problem, and the fix to it was in the kernel I was testing. Indeed it was ... but it didn't fix the bug. With the patch below, I no longer see the bug. Signed-off by: Linas Vepstas Signed-off-by: Jens Axboe Signed-off-by: Adrian Bunk --- block/elevator.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/block/elevator.c b/block/elevator.c index 11e356e440f0..24a926717619 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -365,6 +365,12 @@ void elv_insert(request_queue_t *q, struct request *rq, int where) */ rq->flags |= REQ_SOFTBARRIER; + /* + * Most requeues happen because of a busy condition, + * don't force unplug of the queue for that case. + */ + unplug_it = 0; + if (q->ordseq == 0) { list_add(&rq->queuelist, &q->queue_head); break; @@ -379,11 +385,6 @@ void elv_insert(request_queue_t *q, struct request *rq, int where) } list_add_tail(&rq->queuelist, pos); - /* - * most requeues happen because of a busy condition, don't - * force unplug of the queue for that case. - */ - unplug_it = 0; break; default: -- 2.39.5