NFS: Fix data corruption caused by congestion.

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 <Jacek.Tomaka@poczta.fm>
Fixes: 6df25e58532b ("nfs: remove reliance on bdi congestion")
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 9d82d50ce0b12dc7063f021d4380582633ed419f..4a250f65fa7594216b4ef9cd69ad2e2a7f9b8581 100644 (file)
--- 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,