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Date: Fri, 8 Mar 2024 16:21:12 +0100
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Chandan Babu R <chandanbabu@kernel.org>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH 06/10] ext4: switch to using blk_next_discard_bio
 directly
Message-ID: <20240308152112.GA11963@lst.de>
References: <20240307151157.466013-1-hch@lst.de> <20240307151157.466013-7-hch@lst.de> <ZennjRhWR2PVtoGU@kbusch-mbp>
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In-Reply-To: <ZennjRhWR2PVtoGU@kbusch-mbp>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, Mar 07, 2024 at 09:13:01AM -0700, Keith Busch wrote:
> On Thu, Mar 07, 2024 at 08:11:53AM -0700, Christoph Hellwig wrote:
> > @@ -3840,12 +3840,16 @@ static inline int ext4_issue_discard(struct super_block *sb,
> >  	trace_ext4_discard_blocks(sb,
> >  			(unsigned long long) discard_block, count);
> >  	if (biop) {
> 
> Does this 'if' case even need to exist? It looks unreachable since there
> are only two callers of ext4_issue_discard(), and they both set 'biop'
> to NULL. It looks like the last remaining caller using 'biop' was
> removed with 55cdd0af2bc5ffc ("ext4: get discard out of jbd2 commit
> kthread contex")

Yeah.  I didn't really want to dig so far into code I don't know well
for this series, though :)

> > +		while (blk_next_discard_bio(sb->s_bdev, biop, &sector,
> > +				&nr_sects, GFP_NOFS))
> > +			;
> 
> This pattern is repeated often in this series, so perhaps a helper
> function for this common use case.

Well, it's 2-3 lines vs 1 line for a much better interface.