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Date:   Wed, 23 Mar 2022 07:03:42 +0100
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, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 02/40] btrfs: fix direct I/O read repair for split bios
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On Wed, Mar 23, 2022 at 07:59:15AM +0800, Qu Wenruo wrote:
> Personally speaking, I really hate to add DIO specific value into btrfs_bio.
>
> Hopes we can later turn that btrfs_bio::file_offset into some union for
> other usages.

Agreed.  There is two venues we could explore:

 - ceative use of unions.  Especially with some of my later patches
   adding more fields to struct btrfs_bio this could become possible.
 - adding a btrfs_dio_bio that contains a btrfs_bio.  By the end of
   this series another field (repair_refs) is added, and iter is only
   used for direct I/O, so this might be worthwhile.  But then again
   I think we could eventually kill off iter as well.

So we should eventually do something, but for a non-invasive fix
like this just adding the field for now seems like the most safe
approach.