NFS: Label the dentry with a verifier in nfs_rmdir() and nfs_unlink()

After the success of an operation such as rmdir() or unlink(), we expect
to add the dentry back to the dcache as an ordinary negative dentry.
However in NFS, unless it is labelled with the appropriate verifier for
the parent directory state, then nfs_lookup_revalidate will end up
discarding that dentry and forcing a new lookup.

The fix is to ensure that we relabel the dentry appropriately on
success.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/dir.c

@@ -2197,6 +2197,18 @@ static void nfs_dentry_handle_enoent(struct dentry *dentry)
 		d_delete(dentry);
 }
 
+static void nfs_dentry_remove_handle_error(struct inode *dir,
+					   struct dentry *dentry, int error)
+{
+	switch (error) {
+	case -ENOENT:
+		d_delete(dentry);
+		fallthrough;
+	case 0:
+		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
+	}
+}
+
 int nfs_rmdir(struct inode *dir, struct dentry *dentry)
 {
 	int error;
@@ -2219,6 +2231,7 @@ int nfs_rmdir(struct inode *dir, struct dentry *dentry)
 		up_write(&NFS_I(d_inode(dentry))->rmdir_sem);
 	} else
 		error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
+	nfs_dentry_remove_handle_error(dir, dentry, error);
 	trace_nfs_rmdir_exit(dir, dentry, error);
 
 	return error;
@@ -2288,9 +2301,8 @@ int nfs_unlink(struct inode *dir, struct dentry *dentry)
 	}
 	spin_unlock(&dentry->d_lock);
 	error = nfs_safe_remove(dentry);
-	if (!error || error == -ENOENT) {
-		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
-	} else if (need_rehash)
+	nfs_dentry_remove_handle_error(dir, dentry, error);
+	if (need_rehash)
 		d_rehash(dentry);
 out:
 	trace_nfs_unlink_exit(dir, dentry, error);