Re: [PATCH] 2.6.13-rc1 get_request nastiness

[Jens Axboe <axboe@suse.de>]

On Wed, Jun 29 2005, Hugh Dickins wrote:
> get_request is now expected to be holding on to queue_lock, with interrupts
> disabled, when it returns NULL; but one path forgot that, causing all kinds
> of nastiness under swap load - badness backtraces, strange failures, BUGs.
> 
> Signed-off-by: Hugh Dickins <hugh@veritas.com>
> 
> --- 2.6.13-rc1/drivers/block/ll_rw_blk.c	2005-06-29 11:54:08.000000000 +0100
> +++ linux/drivers/block/ll_rw_blk.c	2005-06-29 14:41:04.000000000 +0100
> @@ -1917,10 +1917,9 @@ get_rq:
>  	 * limit of requests, otherwise we could have thousands of requests
>  	 * allocated with any setting of ->nr_requests
>  	 */
> -	if (rl->count[rw] >= (3 * q->nr_requests / 2)) {
> -		spin_unlock_irq(q->queue_lock);
> +	if (rl->count[rw] >= (3 * q->nr_requests / 2))
>  		goto out;
> -	}
> +

Woops, my bad, sorry about that. I still have to think about that
locking, not directly obvious. Thanks Hugh!

-- 
Jens Axboe