[PATCH] iomap: Move page_done callback under the folio lock

Andreas Gruenbacher
2022-12-13T19:49:35Z

Hi Darrick,

I'd like to get the following iomap change into this merge window. This
only affects gfs2, so I can push it as part of the gfs2 updates if you
don't mind, provided that I'll get your Reviewed-by confirmation.
Otherwise, if you'd prefer to pass this through the xfs tree, could you
please take it?

Thanks,
Andreas

--

Move the ->page_done() call in iomap_write_end() under the folio lock.
This closes a race between journaled data writes and the shrinker in
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 current transaction. The folio lock prevents that from happening.

The only user of ->page_done() is gfs2, so other filesystems are not
affected.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/iomap/buffered-io.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 91ee0b308e13..476c9ed1b333 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -714,12 +714,12 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
i_size_write(iter->inode, pos + ret);
iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
}
+ if (page_ops && page_ops->page_done)
+ page_ops->page_done(iter->inode, pos, ret, &folio->page);
folio_unlock(folio);

if (old_size < pos)
pagecache_isize_extended(iter->inode, old_size, pos);
- if (page_ops && page_ops->page_done)
- page_ops->page_done(iter->inode, pos, ret, &folio->page);
folio_put(folio);

if (ret < len)
--
2.38.1