linux-ext4 - [RFC 0/3] Turn iomap_page_ops into iomap_folio

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Date:   Thu,  1 Dec 2022 17:06:16 +0100
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>
Cc:     Andreas Gruenbacher <agruenba@...hat.com>,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, cluster-devel@...hat.com
Subject: [RFC 0/3] Turn iomap_page_ops into iomap_folio_ops

Hello,

we're seeing a race between journaled data writes and the shrinker on
gfs2.  What's happening is that gfs2_iomap_page_done() is called after
the page has been unlocked, so try_to_free_buffers() can come in and
free the buffers while gfs2_iomap_page_done() is trying to add them to
the transaction.  Not good.

This is a proposal to change iomap_page_ops so that page_prepare()
prepares the write and grabs the locked page, and page_done() unlocks
and puts that page again.  While at it, this also converts the hooks
from pages to folios.

To move the pagecache_isize_extended() call in iomap_write_end() out of
the way, a new folio_may_straddle_isize() helper is introduced that
takes a locked folio.  That is then used when the inode size is updated,
before the folio is unlocked.

I've also converted the other applicable folio_may_straddle_isize()
users, namely generic_write_end(), ext4_write_end(), and
ext4_journalled_write_end().

Any thoughts?

Thanks,
Andreas

Andreas Gruenbacher (3):
  fs: Add folio_may_straddle_isize helper
  iomap: Turn iomap_page_ops into iomap_folio_ops
  gfs2: Fix race between shrinker and gfs2_iomap_folio_done

 fs/buffer.c            |  5 ++---
 fs/ext4/inode.c        | 13 +++++------
 fs/gfs2/bmap.c         | 39 +++++++++++++++++++++++---------
 fs/iomap/buffered-io.c | 51 +++++++++++++++++++++---------------------
 include/linux/iomap.h  | 24 ++++++++++----------
 include/linux/mm.h     |  2 ++
 mm/truncate.c          | 34 ++++++++++++++++++++++++++++
 7 files changed, 110 insertions(+), 58 deletions(-)

-- 
2.38.1