[Cluster-devel] [PATCH 11/30] iomap: add the new iomap_iter model

Darrick J. Wong djwong at kernel.org
Thu Aug 12 18:20:17 UTC 2021

On Thu, Aug 12, 2021 at 08:49:14AM +0200, Christoph Hellwig wrote:
> On Wed, Aug 11, 2021 at 12:17:08PM -0700, Darrick J. Wong wrote:
> > > iter.c is also my preference, but in the end I don't care too much.
> > 
> > Ok.  My plan for this is to change this patch to add the new iter code
> > to apply.c, and change patch 24 to remove iomap_apply.  I'll add a patch
> > on the end to rename apply.c to iter.c, which will avoid breaking the
> > history.
> What history?  There is no shared code, so no shared history and.

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? :)


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