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Date:   Sat, 25 Mar 2023 09:34:26 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Naohiro Aota <Naohiro.Aota@wdc.com>
Cc:     Christoph Hellwig <hch@lst.de>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>, Boris Burkov <boris@bur.io>,
        Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
        "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH 05/11] btrfs: simplify btrfs_extract_ordered_extent
Message-ID: <20230325083426.GB7598@lst.de>
References: <20230324023207.544800-1-hch@lst.de> <20230324023207.544800-6-hch@lst.de> <20230324060725.q2jd6z2wzeytehzb@naota-xeon>
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On Fri, Mar 24, 2023 at 06:07:26AM +0000, Naohiro Aota wrote:
> > -	ret = btrfs_split_ordered_extent(ordered, pre, post);
> > +	ret = btrfs_split_ordered_extent(ordered, len, 0);
> 
> The next patch will overwrite this anyway, but the pre and post are the
> length of new ordered extents which are not covered by the bio. So, giving
> them (len, 0) breaks the semantics so that a new ordered extent is
> allocated for the bio range. They should be (0, ordered_len - len).

Hmm, nothing trips up in my ZNS tests even at this bisection point,
and I don't think it should matter at this stage what part is split
off.  Later we rely on the front being split off and a new
ordered_extent being allocated for the front range covering the
bio.  So maybe this just need to be documented in the commit log?