exportfs: fix 'passing zero to ERR_PTR()' warning

BugLink: https://bugs.launchpad.net/bugs/1864773

[ Upstream commit 909e22e0 ]

Fix a static code checker warning:
  fs/exportfs/expfs.c:171 reconnect_one() warn: passing zero to 'ERR_PTR'

The error path for lookup_one_len_unlocked failure
should set err to PTR_ERR.

Fixes: bbf7a8a3 ("exportfs: move most of reconnect_path to helper function")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/exportfs/expfs.c

@@ -148,6 +148,7 @@ static struct dentry *reconnect_one(struct vfsmount *mnt,
 	mutex_unlock(&parent->d_inode->i_mutex);
 	if (IS_ERR(tmp)) {
 		dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp));
+		err = PTR_ERR(tmp);
 		goto out_err;
 	}
 	if (tmp != dentry) {