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Date:   Fri, 13 Aug 2021 09:29:55 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     "Darrick J. Wong" <djwong@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Shiyang Ruan <ruansy.fnst@fujitsu.com>,
        linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-btrfs@vger.kernel.org, nvdimm@lists.linux.dev,
        cluster-devel@redhat.com
Subject: Re: [PATCH 11/30] iomap: add the new iomap_iter model
Message-ID: <20210813072955.GA27278@lst.de>
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On Thu, Aug 12, 2021 at 11:20:17AM -0700, Darrick J. Wong wrote:
> The history of the gluecode that enables us to walk a bunch of extent
> mappings.  In the beginning it was the _apply function, but now in our
> spectre-weary world, you've switched it to a direct loop to reduce the
> number of indirect calls in the hot path by 30-50%.
> 
> As you correctly point out, there's no /code/ shared by the two
> implementations, but Dave and I would like to preserve the continuity
> from one to the next.
> 
> > > I'll send the updated patches as replies to this series to avoid
> > > spamming the list, since I also have a patchset of bugfixes to send out
> > > and don't want to overwhelm everyone.
> > 
> > Just as a clear statement:  I think this dance is obsfucation and doesn't
> > help in any way.  But if that's what it takes..
> 
> I /would/ appreciate it if you'd rvb (or at least ack) patch 31 so I can
> get the 5.15 iomap changes finalized next week.  Pretty please? :)

I think it is a really stupid idea, so certainly no rvb or ack from me.
If you feel you want to do it this way go ahead, but I do not in any
way approve of it.