linux-ext4 - [RFC 3/3] gfs2: Fix race between shrinker and gfs2_iomap_folio

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Date:   Thu,  1 Dec 2022 17:06:19 +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 3/3] gfs2: Fix race between shrinker and gfs2_iomap_folio_done

In gfs2_iomap_folio_done(), add the modified buffer heads to the current
transaction while the folio is still locked.  Otherwise, the shrinker
can come in and free them before we get to gfs2_page_add_databufs().

Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
 fs/gfs2/bmap.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 18dcaa95408e..d8d9ee843ac9 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -990,18 +990,17 @@ gfs2_iomap_folio_done(struct inode *inode, struct folio *folio,
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_sbd *sdp = GFS2_SB(inode);
 
-	folio_unlock(folio);
-
 	if (!gfs2_is_stuffed(ip))
 		gfs2_page_add_databufs(ip, &folio->page, offset_in_page(pos),
 				       copied);
 
+	folio_unlock(folio);
+	folio_put(folio);
+
 	if (tr->tr_num_buf_new)
 		__mark_inode_dirty(inode, I_DIRTY_DATASYNC);
 
 	gfs2_trans_end(sdp);
-
-	folio_put(folio);
 }
 
 static const struct iomap_folio_ops gfs2_iomap_folio_ops = {
-- 
2.38.1