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authorJens Axboe <axboe@suse.de>2006-05-11 08:20:16 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-11 12:38:59 -0700
commitdac07ec121de66b6be988b14ae2cd9ce45357b21 (patch)
tree95359f17d0857fd52f399cef072097523227d032
parentf358166a9405e4f1d8e50d8f415c26d95505b6de (diff)
downloadlinux-linaro-stable-dac07ec121de66b6be988b14ae2cd9ce45357b21.tar.gz
[BLOCK] 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>
-rw-r--r--block/elevator.c8
-rw-r--r--block/ll_rw_blk.c17
2 files changed, 22 insertions, 3 deletions
diff --git a/block/elevator.c b/block/elevator.c
index 29825792cbd5..8768a367fdde 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -333,6 +333,7 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
{
struct list_head *pos;
unsigned ordseq;
+ int unplug_it = 1;
blk_add_trace_rq(q, rq, BLK_TA_INSERT);
@@ -399,6 +400,11 @@ 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:
@@ -407,7 +413,7 @@ 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 e5041a02e21f..eac48bec1479 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1732,8 +1732,21 @@ 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);