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authorLinas Vepstas <linas@austin.ibm.com>2007-01-23 19:40:54 +0100
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-23 11:01:17 -0800
commit95543179f158b4891c5dc49004853ce081e8d794 (patch)
tree39cc1ae27c53bc7ac7cc6401afc8ecee69b76b0f /block
parent3a7122923e87fc5cdf8affa1845924a0def4657d (diff)
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[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 <linas@austin.ibm.com> Signed-off-by: Jens Axboe <axboe@suse.de> Cc: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'block')
-rw-r--r--block/elevator.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/block/elevator.c b/block/elevator.c
index 536be740ba4..f6dafa8c7c4 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -590,6 +590,12 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
*/
rq->cmd_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;
@@ -604,11 +610,6 @@ 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: