Hi Chris, Jens, Can you look at this, and push upstream if this looks reasonable to you? It fixes a bug I've been tripping over. --linas 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@xxxxxxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxx> Cc: Chris Wright <chrisw@xxxxxxxxxxxx> ---- block/elevator.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) Index: linux-2.6.20-rc4/block/elevator.c =================================================================== --- linux-2.6.20-rc4.orig/block/elevator.c 2007-01-15 14:16:03.000000000 -0600 +++ linux-2.6.20-rc4/block/elevator.c 2007-01-15 14:20:04.000000000 -0600 @@ -590,6 +590,12 @@ void elv_insert(request_queue_t *q, stru */ 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, stru } 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: - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
