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Date:   Sat, 18 Mar 2023 07:42:06 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Christoph Hellwig <hch@lst.de>, Jan Kara <jack@suse.cz>,
        Ming Lei <ming.lei@redhat.com>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Johannes Thumshirn <johannes.thumshirn@wdc.com>
Subject: Re: [PATCH 2/2] block: Split and submit bios in LBA order
Message-ID: <20230318064206.GE24880@lst.de>
References: <20230317195938.1745318-1-bvanassche@acm.org> <20230317195938.1745318-3-bvanassche@acm.org>
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On Fri, Mar 17, 2023 at 12:59:38PM -0700, Bart Van Assche wrote:
> @@ -380,8 +380,9 @@ struct bio *__bio_split_to_limits(struct bio *bio,
>  		blkcg_bio_issue_init(split);
>  		bio_chain(split, bio);
>  		trace_block_split(split, bio->bi_iter.bi_sector);
> -		submit_bio_noacct(bio);
> -		return split;
> +		submit_bio_noacct(split);
> +		*nr_segs = bio_nr_segments(lim, bio);

Please add this recalculation into the individual bio_split_*
functions, as the recalculation is only needed for regular read/write
bios.  It might also be slightly cheaper to just continue the segment
calculation there in the existing loop instead of starting a new
one after the split.