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Date:   Fri, 4 Nov 2022 20:06:49 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Vishal Moola <vishal.moola@gmail.com>,
        linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
        ceph-devel@vger.kernel.org, linux-cifs@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net,
        cluster-devel@redhat.com, linux-nilfs@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 04/23] page-writeback: Convert write_cache_pages() to use
 filemap_get_folios_tag()
Message-ID: <Y2Vw2UBkti7MeG5U@casper.infradead.org>
References: <20220901220138.182896-1-vishal.moola@gmail.com>
 <20220901220138.182896-5-vishal.moola@gmail.com>
 <20221018210152.GH2703033@dread.disaster.area>
 <Y2RAdUtJrOJmYU4L@fedora>
 <20221104003235.GZ2703033@dread.disaster.area>
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On Fri, Nov 04, 2022 at 11:32:35AM +1100, Dave Chinner wrote:
> At minimum, it needs to be documented, though I'd much prefer that
> we explicitly duplicate write_cache_pages() as write_cache_folios()
> with a callback that takes a folio and change the code to be fully
> multi-page folio safe. Then filesystems that support folios (and
> large folios) natively can be passed folios without going through
> this crappy "folio->page, page->folio" dance because the writepage
> APIs are unaware of multi-page folio constructs.

There are a lot of places which go through the folio->page->folio
dance, and this one wasn't even close to the top of my list.  That
said, it has a fairly small number of callers -- ext4, fuse, iomap,
mpage, nfs, orangefs.  So Vishal, this seems like a good project for you
to take on next -- convert write_cache_pages() to write_cache_folios()
and writepage_t to write_folio_t.