[PATCH 1/1] nfs: don't skip revalidate on directory delegation when attrs flagged stale

[Tom Haynes <loghyr@gmail.com>]

On a local directory mutation (rename/create/unlink) the client marks
CHANGE / MTIME / CTIME as invalid in NFS_I(dir)->cache_validity.  When
a subsequent stat(2) enters __nfs_revalidate_inode() and finds a
directory delegation held, the function currently early-exits and
returns the cached (now stale) mtime to userspace without sending a
GETATTR RPC.

Keep the early-exit for the fast path, but take the RPC when CHANGE,
MTIME, or CTIME are already marked invalid.  The delegation alone is
not a guarantee of cached-attr freshness once the code itself has
flagged the cache as stale.

Assisted-by: Claude:claude-opus-4-7 [bpftrace] [tshark]
Signed-off-by: Tom Haynes <loghyr@gmail.com>
---
 fs/nfs/inode.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 98a8f0de1199..936bc329f462 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1390,7 +1390,11 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 		status = pnfs_sync_inode(inode, false);
 		if (status)
 			goto out;
-	} else if (nfs_have_directory_delegation(inode)) {
+	} else if (nfs_have_directory_delegation(inode) &&
+		   !(NFS_I(inode)->cache_validity &
+		     (NFS_INO_INVALID_CHANGE |
+		      NFS_INO_INVALID_MTIME  |
+		      NFS_INO_INVALID_CTIME))) {
 		status = 0;
 		goto out;
 	}
-- 
2.53.0