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Date:   Mon, 25 Apr 2022 13:09:28 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc:     Christoph Hellwig <hch@lst.de>, Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>, Qu Wenruo <wqu@suse.com>,
        Naohiro Aota <naohiro.aota@wdc.com>,
        linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 03/10] btrfs: split btrfs_submit_data_bio
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On Mon, Apr 25, 2022 at 05:37:40PM +0800, Qu Wenruo wrote:
> Oh, please don't completely get rid of btrfs_bio, even just for writes.
>
> The btrfs_bio::iter is pretty important for us to grab the original
> logical bytenr of a bio.
> As bio::bi_iter can be modified by lower level (does dm modifies it
> too?), or btrfs itself.
>
> In fact, my incoming updated btrfs repair repair code heavily rely on
> btrfs_bio::iter, both read and write, to grab the original logical
> bytenr of the bio.

Then it's doing the wrong thing.  I actually have a series to remove
it entirely.