when AOP_WRITEPAGE_ACTIVATE is returned (as NFS does when it detects
congestion) it is important that the folio 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.  Prior to 6.3 the patch
is different as it needs to mention "page", not "folio".

Reported-and-tested-by: Jacek Tomaka <redacted>
Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
Signed-off-by: NeilBrown <redacted>
---
 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 b664caea8b4e..9e345d3c305a 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c

@@ -668,8 +668,10 @@ static int nfs_writepage_locked(struct folio *folio,
 	int err;
 
 	if (wbc->sync_mode == WB_SYNC_NONE &&
-	    NFS_SERVER(inode)->write_congested)
+	    NFS_SERVER(inode)->write_congested) {
+		folio_redirty_for_writepage(wbc, folio);
 		return AOP_WRITEPAGE_ACTIVATE;
+	}
 
 	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
 	nfs_pageio_init_write(&pgio, inode, 0, false,

-- 
2.43.0