diff options
| author | Jens Axboe <axboe@suse.de> | 2006-05-11 08:20:16 +0200 |
|---|---|---|
| committer | Chris Wright <chrisw@sous-sol.org> | 2006-05-20 15:00:31 -0700 |
| commit | 7984c7b5a2ccd821caeab3d751e0941ca5e8b8d1 (patch) | |
| tree | 8efd3960a7f1b6d1aad1353deb88ae2cbc5bc67f /block/elevator.c | |
| parent | 0cf72aa68c30845d4ac076909af4edd6e4cdaab9 (diff) | |
[PATCH] limit request_fn recursion
Don't recurse back into the driver even if the unplug threshold is met,
when the driver asks for a requeue. This is both silly from a logical
point of view (requeues typically happen due to driver/hardware
shortage), and also dangerous since we could hit an endless request_fn
-> requeue -> unplug -> request_fn loop and crash on stack overrun.
Also limit blk_run_queue() to one level of recursion, similar to how
blk_start_queue() works.
This patch fixed a real problem with SLES10 and lpfc, and it could hit
any SCSI lld that returns non-zero from it's ->queuecommand() handler.
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Diffstat (limited to 'block/elevator.c')
| -rw-r--r-- | block/elevator.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/block/elevator.c b/block/elevator.c index 24b702d649a9..ef1e606ab166 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -314,6 +314,7 @@ void elv_insert(request_queue_t *q, struct request *rq, int where) { struct list_head *pos; unsigned ordseq; + int unplug_it = 1; rq->q = q; @@ -378,6 +379,11 @@ 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: @@ -386,7 +392,7 @@ void elv_insert(request_queue_t *q, struct request *rq, int where) BUG(); } - if (blk_queue_plugged(q)) { + if (unplug_it && blk_queue_plugged(q)) { int nrq = q->rq.count[READ] + q->rq.count[WRITE] - q->in_flight; |