Re: [PATCH] blk-mq: Make it safe to call blk_mq_quiesce_queue_nowait() from an interrupt handler

[Ming Lei <ming.lei@redhat.com>]

On Wed, Jun 21, 2017 at 09:42:36AM +0800, Ming Lei wrote:
> On Tue, Jun 20, 2017 at 09:40:20AM -0700, Bart Van Assche wrote:
> > Since blk_mq_quiesce_queue_nowait() can be called from interrupt
> > context, make this safe. Since this function is not in the hot
> > path, uninline it. Untested.
> > 
> > Fixes: commit f4560ffe8cec ("blk-mq: use QUEUE_FLAG_QUIESCED to quiesce queue")
> > Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> > Cc: Ming Lei <ming.lei@redhat.com>
> > Cc: Hannes Reinecke <hare@suse.com>
> > Cc: Martin K. Petersen <martin.petersen@oracle.com>
> > ---
> >  block/blk-mq.c         | 14 ++++++++++++++
> >  include/linux/blk-mq.h | 10 +---------
> >  2 files changed, 15 insertions(+), 9 deletions(-)
> > 
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index 1c4f1f4978c6..92faf340dc92 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -153,6 +153,20 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
> >  }
> >  EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
> >  
> > +/*
> > + * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
> > + * mpt3sas driver such that this function can be removed.
> > + */
> > +void blk_mq_quiesce_queue_nowait(struct request_queue *q)
> > +{
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(q->queue_lock, flags);
> > +	queue_flag_set(QUEUE_FLAG_QUIESCED, q);
> > +	spin_unlock_irqrestore(q->queue_lock, flags);
> > +}
> > +EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
> > +
> >  /**
> >   * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
> >   * @q: request queue.
> > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> > index 366b83cee955..23d32ff0b462 100644
> > --- a/include/linux/blk-mq.h
> > +++ b/include/linux/blk-mq.h
> > @@ -266,15 +266,7 @@ int blk_mq_reinit_tagset(struct blk_mq_tag_set *set);
> >  int blk_mq_map_queues(struct blk_mq_tag_set *set);
> >  void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
> >  
> > -/*
> > - * FIXME: this helper is just for working around mpt3sas.
> > - */
> > -static inline void blk_mq_quiesce_queue_nowait(struct request_queue *q)
> > -{
> > -	spin_lock_irq(q->queue_lock);
> > -	queue_flag_set(QUEUE_FLAG_QUIESCED, q);
> > -	spin_unlock_irq(q->queue_lock);
> > -}
> > +void blk_mq_quiesce_queue_nowait(struct request_queue *q);
> >  
> >  /*
> >   * Driver command data is immediately after the request. So subtract request
> > -- 
> > 2.13.1
> > 
> 
> Looks fine,
> 
> Reviewed-by: Ming Lei <ming.lei@redhat.com>

Also we should save/restore irq flags in blk_mq_unquiesce_queue()
since scsi_start_queue() does that too, could you fix the two
in this patch?


Thanks,
Ming