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 | |
| 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')
| -rw-r--r-- | block/elevator.c | 8 | ||||
| -rw-r--r-- | block/ll_rw_blk.c | 17 |
2 files changed, 22 insertions, 3 deletions
diff --git a/block/elevator.c b/block/elevator.c index 24b702d649a..ef1e606ab16 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; diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index 0ef2971a9e8..cd995c3fd5d 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -1719,8 +1719,21 @@ void blk_run_queue(struct request_queue *q) spin_lock_irqsave(q->queue_lock, flags); blk_remove_plug(q); - if (!elv_queue_empty(q)) - q->request_fn(q); + + /* + * Only recurse once to avoid overrunning the stack, let the unplug + * handling reinvoke the handler shortly if we already got there. + */ + if (!elv_queue_empty(q)) { + if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) { + q->request_fn(q); + clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags); + } else { + blk_plug_device(q); + kblockd_schedule_work(&q->unplug_work); + } + } + spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL(blk_run_queue); |