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From: "NeilBrown" <neilb@suse.de>
To: stable@vger.kernel.org, Trond Myklebust <trond.myklebust@hammerspace.com>,
 Anna Schumaker <anna@kernel.org>
Cc: linux-nfs@vger.kernel.org,  Jacek Tomaka <Jacek.Tomaka@poczta.fm>
Subject: [PATCH stable 6.1] NFS: Fix data corruption caused by congestion.
Date: Wed, 28 Feb 2024 10:25:49 +1100
Message-id: <170907634991.24797.14120500624611379941@noble.neil.brown.name>


when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects
congestion) it is important that the page is redirtied.
nfs_writepage_locked() doesn't do this, so files can become corrupted as
writes can be lost.

Note that this is not needed in v6.8 as AOP_WRITEPAGE_ACTIVATE cannot be
returned.  It is needed for kernels v5.18..v6.7.  From 6.3 onward the patch
is different as it needs to mention "folio", not "page".

Reported-and-tested-by: Jacek Tomaka <Jacek.Tomaka@poczta.fm>
Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/nfs/write.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index f41d24b54fd1..6a0606668417 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -667,8 +667,10 @@ static int nfs_writepage_locked(struct page *page,
 	int err;
 
 	if (wbc->sync_mode == WB_SYNC_NONE &&
-	    NFS_SERVER(inode)->write_congested)
+	    NFS_SERVER(inode)->write_congested) {
+		redirty_page_for_writepage(wbc, page);
 		return AOP_WRITEPAGE_ACTIVATE;
+	}
 
 	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
 	nfs_pageio_init_write(&pgio, inode, 0,
-- 
2.43.0