Re: [PATCH] Use list_splice for blk_abort_queue

[Jens Axboe <jens.axboe@oracle.com>]

On Fri, Feb 27 2009, Hannes Reinecke wrote:
> Hi Jens,
>
> Jens Axboe wrote:
>> On Fri, Feb 27 2009, Hannes Reinecke wrote:
>>> blk_abort_queue takes the queue_lock with spinlock_irqsave and walks
>>> the timer_list with list_for_each_entry_safe. Since a path to a SCSI
>>> device just failed, the rport state is FC_PORTSTATE_BLOCKED. This
>>> rport state triggers blk_add_timer(), which in turn calls
>>> list_add_tail() to move the request to the end of timer_list. Thus,
>>> the list_for_each_XXX loop never reaches the end of the timer_list.
>>> By using list_splice_init() we're breaking the loop and process only
>>> the requests present on the timeout_list when blk_abort_queue() is
>>> called.
>>>
>>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>>> Tested-by: Christof Schmitt <christof.schmitt@de.ibm.com>
>>> ---
>>>  block/blk-timeout.c |    5 ++++-
>>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/block/blk-timeout.c b/block/blk-timeout.c
>>> index a095353..67bcc3f 100644
>>> --- a/block/blk-timeout.c
>>> +++ b/block/blk-timeout.c
>>> @@ -209,12 +209,15 @@ void blk_abort_queue(struct request_queue *q)
>>>  {
>>>  	unsigned long flags;
>>>  	struct request *rq, *tmp;
>>> +	LIST_HEAD(list);
>>>
>>>  	spin_lock_irqsave(q->queue_lock, flags);
>>>
>>>  	elv_abort_queue(q);
>>>
>>> -	list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
>>> +	list_splice_init(&q->timeout_list, &list);
>>> +
>>> +	list_for_each_entry_safe(rq, tmp, &list, timeout_list)
>>>  		blk_abort_request(rq);
>>>
>>>  	spin_unlock_irqrestore(q->queue_lock, flags);
>>> --
>>> 1.5.3.2
>>>
>>
>> Hannes, this fix has been in mainline for about 10 days.
>>
> Ah, sorry. Missed that one.
> I'm just about to catch up with unread mails, and you said something
> about 'the original author should resend the patch'.
> Which I did.

Yep, I did say that. But after a few days I figured you were probably
away or something, so I hacked up a changelog myself and put it in
there. It was already tested good and it makes sense.

-- 
Jens Axboe