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Date:   Sun, 20 Feb 2022 04:23:50 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Stefan Roesch <shr@fb.com>, io-uring@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [PATCH v2 04/13] fs: split off __alloc_page_buffers function
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On Fri, Feb 18, 2022 at 11:35:10PM -0800, Christoph Hellwig wrote:
> Err, hell no.  Please do not add any new functionality to the legacy
> buffer head code.  If you want new features do that on the
> non-bufferhead iomap code path only please.

I think "first convert the block device code from buffer_heads to iomap"
might be a bit much of a prerequisite.  I think running ext4 on top of a
block device still requires buffer_heads, for example (I tried to convert
the block device to use mpage in order to avoid creating buffer_heads
when possible, and ext4 stopped working.  I didn't try too hard to debug
it as it was a bit of a distraction at the time).