Re: [PATCH] null_blk: cleanup null_init_tag_set

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

On Fri, Jul 15, 2022 at 02:11:21PM +0000, Vincent Fu wrote:
> > -----Original Message-----
> > From: Ming Lei [mailto:ming.lei@redhat.com]
> > Sent: Thursday, July 14, 2022 11:19 PM
> > To: Jens Axboe <axboe@kernel.dk>
> > Cc: linux-block@vger.kernel.org; Ming Lei <ming.lei@redhat.com>;
> > Vincent Fu <vincent.fu@samsung.com>
> > Subject: [PATCH] null_blk: cleanup null_init_tag_set
> > 
> > The passed 'nullb' can be NULL, so cause null ptr reference.
> > 
> > Fix the issue, meantime cleanup null_init_tag_set for avoiding to add
> > similar issue in future.
> > 
> > Cc: Vincent Fu <vincent.fu@samsung.com>
> > Fixes: 37ae152c7a0d ("null_blk: add configfs variables for 2 options")
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  drivers/block/null_blk/main.c | 49 ++++++++++++++++++++++-----------
> > --
> >  1 file changed, 31 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> > index c955a07dba2d..a08856b121b3 100644
> > --- a/drivers/block/null_blk/main.c
> > +++ b/drivers/block/null_blk/main.c
> > @@ -1898,31 +1898,44 @@ static int null_gendisk_register(struct nullb
> > *nullb)
> > 
> >  static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set
> > *set)
> >  {
> > +	unsigned int flags = BLK_MQ_F_SHOULD_MERGE;
> > +	int hw_queues, numa_node;
> > +	unsigned int queue_depth;
> >  	int poll_queues;
> > 
> > +	if (nullb) {
> > +		hw_queues = nullb->dev->submit_queues;
> > +		poll_queues = nullb->dev->poll_queues;
> > +		queue_depth = nullb->dev->hw_queue_depth;
> > +		numa_node = nullb->dev->home_node;
> > +		if (nullb->dev->no_sched)
> > +			flags |= BLK_MQ_F_NO_SCHED;
> > +		if (nullb->dev->shared_tag_bitmap)
> > +			flags |= BLK_MQ_F_TAG_HCTX_SHARED;
> > +		if (nullb->dev->blocking)
> > +			flags |= BLK_MQ_F_BLOCKING;
> > +	} else {
> > +		hw_queues = g_submit_queues;
> > +		poll_queues = g_poll_queues;
> > +		queue_depth = g_hw_queue_depth;
> > +		numa_node = g_home_node;
> > +		if (g_blocking)
> > +			flags |= BLK_MQ_F_BLOCKING;
> > +	}
> > +
> 
> Ming, thank you for fixing the mess I created.
> 
> I believe that even when 'nullb' is NULL we should still set the
> BLK_MQ_F_NO_SCHED and BLK_MQ_F_TAG_HCTX_SHARED flags based on the values of
> g_no_sched and g_shared_tag_bitmap, respectively. Is that not right?

Yeah, it is right, and I have covered it in V2.

Thanks,
Ming