NAK: [PATCH 3/3 Xenial SRU] blk-mq: End unstarted requests on dying queue

[Tim Gardner]

On 05/26/2016 07:50 AM, Tim Gardner wrote:
> On 05/26/2016 06:58 AM, Christopher Arges wrote:
>> On Wed, May 25, 2016 at 08:47:33AM -0600, Tim Gardner wrote:
>>> From: Keith Busch <keith.busch at intel.com>
>>>
>>> BugLink: http://bugs.launchpad.net/bugs/1581034
>>>
>>> Go directly to ending a request if it wasn't started. Previously, completing a
>>> request may invoke a driver callback for a request it didn't initialize.
>>>
>>> Signed-off-by: Keith Busch <keith.busch at intel.com>
>>> Reviewed-by: Sagi Grimberg <sagig at mellanox.com>
>>> Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
>>> Acked-by: Christoph Hellwig <hch at lst.de>
>>> Signed-off-by: Jens Axboe <axboe at fb.com>
>>> (back ported from commit a59e0f5795fe52dad42a99c00287e3766153b312)
>>> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
>>> ---
>>>  block/blk-mq.c | 6 ++++--
>>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>>> index 93a4e19..3989b2d 100644
>>> --- a/block/blk-mq.c
>>> +++ b/block/blk-mq.c
>>> @@ -599,8 +599,10 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
>>>  		 * If a request wasn't started before the queue was
>>>  		 * marked dying, kill it here or it'll go unnoticed.
>>>  		 */
>>> -		if (unlikely(blk_queue_dying(rq->q)))
>>> -			blk_mq_complete_request(rq, -EIO);
>>> +		if (unlikely(blk_queue_dying(rq->q))) {
>>> +			rq->errors = -EIO;
>>> +			blk_mq_complete_request(rq, rq->errors);
>>> +
>>
>> Why does this call blk_mq_complete_request instead of blk_mq_end_request per the
>> original commit?
>>
> This patch ('blk-mq: End unstarted requests on dying queue') came after
> commit a59e0f5795fe52dad42a99c00287e3766153b312 ('blk-mq: End unstarted
> requests on dying queue') which changes the call from
> blk_mq_complete_request(rq, -EIO) to blk_mq_end_request(rq, rq->errors).
> If you follow the chain of logic, blk_mq_complete_request() calls
> blk_mq_end_request() within the semantics of the driver. Calling
> blk_mq_end_request() might have unintended side effects. I chose to
> implement the simplest backport possible.
> 

Ugh, that was totally garbled. I'll resumbit with v2.
-- 
Tim Gardner tim.gardner at canonical.com