linux-kernel - Re: New warning in nvme_setup

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Date:   Fri, 16 Jul 2021 18:41:52 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Oleksandr Natalenko <oleksandr@...alenko.name>
Cc:     linux-kernel@...r.kernel.org, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        linux-nvme@...ts.infradead.org,
        David Jeffery <djeffery@...hat.com>,
        Laurence Oberman <loberman@...hat.com>,
        Paolo Valente <paolo.valente@...aro.org>,
        Jan Kara <jack@...e.cz>, Sasha Levin <sashal@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Keith Busch <kbusch@...nel.org>
Subject: Re: New warning in nvme_setup_discard

On Fri, Jul 16, 2021 at 12:03:43PM +0200, Oleksandr Natalenko wrote:
> Hello.
> 
> On pátek 16. července 2021 11:33:05 CEST Ming Lei wrote:
> > Can you test the following patch?
> 
> Sure, building it at the moment, and will give it a try. Also please see my 
> comments and questions below.
> 
> > 
> > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> > index 727955918563..673a634eadd9 100644
> > --- a/block/bfq-iosched.c
> > +++ b/block/bfq-iosched.c
> > @@ -2361,6 +2361,9 @@ static int bfq_request_merge(struct request_queue *q,
> > struct request **req, __rq = bfq_find_rq_fmerge(bfqd, bio, q);
> >  	if (__rq && elv_bio_merge_ok(__rq, bio)) {
> >  		*req = __rq;
> > +
> > +		if (blk_discard_mergable(__rq))
> > +			return ELEVATOR_DISCARD_MERGE;
> >  		return ELEVATOR_FRONT_MERGE;
> >  	}
> > 
> > diff --git a/block/blk-merge.c b/block/blk-merge.c
> > index a11b3b53717e..f8707ff7e2fc 100644
> > --- a/block/blk-merge.c
> > +++ b/block/blk-merge.c
> > @@ -705,22 +705,6 @@ static void blk_account_io_merge_request(struct request
> > *req) }
> >  }
> > 
> > -/*
> > - * Two cases of handling DISCARD merge:
> > - * If max_discard_segments > 1, the driver takes every bio
> > - * as a range and send them to controller together. The ranges
> > - * needn't to be contiguous.
> > - * Otherwise, the bios/requests will be handled as same as
> > - * others which should be contiguous.
> > - */
> > -static inline bool blk_discard_mergable(struct request *req)
> > -{
> > -	if (req_op(req) == REQ_OP_DISCARD &&
> > -	    queue_max_discard_segments(req->q) > 1)
> > -		return true;
> > -	return false;
> > -}
> > -
> >  static enum elv_merge blk_try_req_merge(struct request *req,
> >  					struct request *next)
> >  {
> > diff --git a/block/elevator.c b/block/elevator.c
> > index 52ada14cfe45..a5fe2615ec0f 100644
> > --- a/block/elevator.c
> > +++ b/block/elevator.c
> > @@ -336,6 +336,9 @@ enum elv_merge elv_merge(struct request_queue *q, struct
> > request **req, __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
> >  	if (__rq && elv_bio_merge_ok(__rq, bio)) {
> >  		*req = __rq;
> > +
> > +		if (blk_discard_mergable(__rq))
> > +			return ELEVATOR_DISCARD_MERGE;
> >  		return ELEVATOR_BACK_MERGE;
> >  	}
> > 
> > diff --git a/block/mq-deadline-main.c b/block/mq-deadline-main.c
> > index 6f612e6dc82b..294be0c0db65 100644
> > --- a/block/mq-deadline-main.c
> > +++ b/block/mq-deadline-main.c
> 
> I had to adjust this against v5.13 because there's no mq-deadline-main.c, only 
> mq-deadline.c (due to Bart series, I assume). I hope this is fine as the patch 
> applies cleanly.
> 
> > @@ -677,6 +677,8 @@ static int dd_request_merge(struct request_queue *q,
> > struct request **rq,
> > 
> >  		if (elv_bio_merge_ok(__rq, bio)) {
> >  			*rq = __rq;
> > +			if (blk_discard_mergable(__rq))
> > +				return ELEVATOR_DISCARD_MERGE;
> >  			return ELEVATOR_FRONT_MERGE;
> >  		}
> >  	}
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index 3177181c4326..87f00292fd7a 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -1521,6 +1521,22 @@ static inline int
> > queue_limit_discard_alignment(struct queue_limits *lim, sector return
> > offset << SECTOR_SHIFT;
> >  }
> > 
> > +/*
> > + * Two cases of handling DISCARD merge:
> > + * If max_discard_segments > 1, the driver takes every bio
> > + * as a range and send them to controller together. The ranges
> > + * needn't to be contiguous.
> > + * Otherwise, the bios/requests will be handled as same as
> > + * others which should be contiguous.
> > + */
> > +static inline bool blk_discard_mergable(struct request *req)
> > +{
> > +	if (req_op(req) == REQ_OP_DISCARD &&
> > +	    queue_max_discard_segments(req->q) > 1)
> > +		return true;
> > +	return false;
> > +}
> > +
> >  static inline int bdev_discard_alignment(struct block_device *bdev)
> >  {
> >  	struct request_queue *q = bdev_get_queue(bdev);
> 
> Do I understand correctly that this will be something like:
> 
> Fixes: 2705dfb209 ("block: fix discard request merge")
> 
> ?
> 
> Because as the bisection progresses, I've bumped into this commit only. 
> Without it the issue is not reproducible, at least so far.

It could be.

So can you just test v5.14-rc1?


Thanks,
Ming