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Date:   Tue, 24 May 2022 14:08:47 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc:     Christoph Hellwig <hch@lst.de>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 8/8] btrfs: use btrfs_bio_for_each_sector in
 btrfs_check_read_dio_bio
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On Tue, May 24, 2022 at 04:21:38PM +0800, Qu Wenruo wrote:
>> The things like resetting initial_mirror, making the naming "initial"
>> meaningless.
>> And the reset on the length part is also very quirky.
>
> In fact, if you didn't do the initial_mirror and length change (which is
> a big disaster of readability, to change iterator in a loop, at least to
> me),

So what is the big problem there?  Do I need more extensive documentation
or as there anything in this concept that is just too confusing.

> and rely on the VFS re-read behavior to fall back to sector by
> secot read, I would call it better readability...

I don't think relying on undocumented VFS behavior is a good idea.  It
will also not work for direct I/O if any single direct I/O bio has
ever more than a single page, which is something btrfs badly needs
if it wants to get any kind of performance out of direct I/O.