With a write delegation, the server permits the client to buffer writes
and associated metadata updates (including file size changes) locally and
defer propagating them to the server. As a result, the server-reported
GETATTR size may legitimately lag behind the client’s cached size for the
duration of the delegation, so it must not be treated as authoritative.

This patch modifies nfs_wcc_update_inode to update the cached inode size
only when the client does not hold a write delegation or the cache_validity
of the nfs_inode has the NFS_INO_INVALID_SIZE bit set.

Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 fs/nfs/inode.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

v2:
  . added missing 'NFS:' on Subject line.

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 4786343eeee0..21161ebbd953 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c

@@ -1649,8 +1649,11 @@ static void nfs_wcc_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 			&& (fattr->valid & NFS_ATTR_FATTR_SIZE)
 			&& i_size_read(inode) == nfs_size_to_loff_t(fattr->pre_size)
 			&& !nfs_have_writebacks(inode)) {
-		trace_nfs_size_wcc(inode, fattr->size);
-		i_size_write(inode, nfs_size_to_loff_t(fattr->size));
+		if ((!nfs_have_write_delegation(inode)) ||
+			(NFS_I(inode)->cache_validity & NFS_INO_INVALID_SIZE)) {
+			trace_nfs_size_wcc(inode, fattr->size);
+			i_size_write(inode, nfs_size_to_loff_t(fattr->size));
+		}
 	}
 }
 

-- 
2.47.3