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Date:   Sat, 18 Mar 2023 07:25:10 +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,
        Christoph Hellwig <hch@lst.de>,
        Keith Busch <kbusch@kernel.org>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Josef Bacik <josef@toxicpanda.com>,
        Johannes Thumshirn <johannes.thumshirn@wdc.com>,
        David Sterba <dsterba@suse.com>
Subject: Re: [PATCH] block: Support splitting REQ_OP_ZONE_APPEND bios
Message-ID: <20230318062510.GA24880@lst.de>
References: <20230317195036.1743712-1-bvanassche@acm.org>
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On Fri, Mar 17, 2023 at 12:50:35PM -0700, Bart Van Assche wrote:
> Make it easier for filesystems to submit zone append bios that exceed
> the block device limits by adding support for REQ_OP_ZONE_APPEND in
> bio_split(). See also commit 0512a75b98f8 ("block: Introduce
> REQ_OP_ZONE_APPEND").

You can't do that.  ZONE_APPEND reports the written sector in bi_sector,
so it can't be split.

> This patch is a bug fix for commit d5e4377d5051 because that commit
> introduces a call to bio_split() for zone append bios without adding
> support for splitting REQ_OP_ZONE_APPEND bios in bio_split().

That commit never splits ZONE_APPEND bios, and it pre-splits bios
about to become ZONE_APPEND bios specifically using bio_split_rw
instead of bio_split.