linux-kernel - Re: [PATCH v2 06/11] blk-mq: Pass driver tags to blk_mq_clear_rq

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Message-ID: <YSMPEGmHP8YljCnV@T590>
Date:   Mon, 23 Aug 2021 10:59:28 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     John Garry <john.garry@...wei.com>
Cc:     axboe@...nel.dk, jejb@...ux.ibm.com, martin.petersen@...cle.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, kashyap.desai@...adcom.com,
        hare@...e.de
Subject: Re: [PATCH v2 06/11] blk-mq: Pass driver tags to
 blk_mq_clear_rq_mapping()

On Thu, Aug 19, 2021 at 08:32:20AM +0100, John Garry wrote:
> On 19/08/2021 01:39, Ming Lei wrote:
> > > That's intentional, as we have from later patch:
> > > 
> > > void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
> > > unsigned int hctx_idx)
> > > {
> > > 	struct blk_mq_tags *drv_tags;
> > > 	struct page *page;
> > > 
> > > +	if (blk_mq_is_sbitmap_shared(set->flags))
> > > +		drv_tags = set->shared_sbitmap_tags;
> > > +	else
> > > 		drv_tags = set->tags[hctx_idx];
> > > 
> > > 	...
> > > 
> > > 	blk_mq_clear_rq_mapping(drv_tags, tags);
> > > 
> > > }
> > > 
> > > And it's just nice to not re-indent later.
> > But this way is weird, and I don't think checkpatch.pl is happy with
> > it.
> 
> There is the idea to try to not remove/change code earlier in a series - I
> am taking it to an extreme! I can stop.
> 
> On another related topic, how about this change also:
> 
> ---8<---
> void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
> 			     struct blk_mq_tags *tags)
>  {
> 
> +	/* There is no need to clear a driver tags own mapping */
> +	if (drv_tags == tags)
> +		return;
> --->8---

The change itself is correct, and no need to clear driver tags
->rq[] since all request queues have been cleaned up when freeing
tagset.


Thanks,
Ming