Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=95543179f158b4891c5dc49004853ce081e8d794
Commit: 95543179f158b4891c5dc49004853ce081e8d794
Parent: 3a7122923e87fc5cdf8affa1845924a0def4657d
Author: Linas Vepstas <[EMAIL PROTECTED]>
AuthorDate: Tue Jan 23 19:40:54 2007 +0100
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue Jan 23 11:01:17 2007 -0800
[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 <[EMAIL PROTECTED]>
Signed-off-by: Jens Axboe <[EMAIL PROTECTED]>
Cc: Chris Wright <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
block/elevator.c | 11 ++++++-----
1 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/block/elevator.c b/block/elevator.c
index 536be74..f6dafa8 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:
-
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