linux-kernel - [PATCH] block: In blk_execute_rq_nowait, init rq->end

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Message-ID: <CAFR8ueeU0z69zAHxJULohZoJ3ONX-ku2mzmUiUatQ=n-V4Eq+w@mail.gmail.com>
Date:	Wed, 6 Jun 2012 23:27:43 -0700
From:	Muthu Kumar <muthu.lkml@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jens Axboe <axboe@...nel.dk>,
	James.Bottomley@...senpartnership.com, linux-kernel@...r.kernel.org
Subject: [PATCH] block: In blk_execute_rq_nowait, init rq->end_io before
 checking for dead queue.

On Wed, Jun 6, 2012 at 11:16 PM, Tejun Heo <tj@...nel.org> wrote:
> Sorry to be nit-picky but Jens would appreciate proper subject and it
> would also be nice to mention the locking change (or even separate
> that into a separate patch).

No problem. Changed the subject and also added the info about queue
lock in the description. Please check.

-----------------------
blk-exec.c: In blk_execute_rq_nowait(), if the queue is dead, call to
done() routine is not made. That will result in blk_execute_rq() stuck
in wait_for_completion(). Avoid this by initializing rq->end_io to
done() routine before we check for dead queue.

Also, in case of dead queue, call the completion routine with queue->lock held.


Signed-off-by: Muthukumar Ratty <muthur@...il.com>
CC: Tejun Heo <tj@...nel.org>
CC: Jens Axboe <axboe@...nel.dk>
CC: James Bottomley <James.Bottomley@...senpartnership.com>

-----------------------

diff --git a/block/blk-exec.c b/block/blk-exec.c
index fb2cbd5..284bf56 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -53,16 +53,17 @@ void blk_execute_rq_nowait(struct request_queue
*q, struct gendisk *bd_disk,
        WARN_ON(irqs_disabled());
        spin_lock_irq(q->queue_lock);

+       rq->rq_disk = bd_disk;
+       rq->end_io = done;
+
        if (unlikely(blk_queue_dead(q))) {
-               spin_unlock_irq(q->queue_lock);
                rq->errors = -ENXIO;
                if (rq->end_io)
                        rq->end_io(rq, rq->errors);
+               spin_unlock_irq(q->queue_lock);
                return;
        }

-       rq->rq_disk = bd_disk;
-       rq->end_io = done;
        __elv_add_request(q, rq, where);
        __blk_run_queue(q);
        /* the queue is stopped so it won't be run */


------------------------------------







>
> Thanks.
>
> --
> tejun

View attachment "blk-exec-assign-endio-before-queue-dead-check.patch" of type "text/x-diff" (1245 bytes)