ceph: fix a NULL vs IS_ERR() check when calling ceph_lookup_inode()

The ceph_lookup_inode() function returns error pointers.  It never
returns NULL.

Fixes: aa87052 ("ceph: fix incorrectly showing the .snap size for stat")
Signed-off-by: Dan Carpenter <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Xiubo Li <[email protected]>
Signed-off-by: Ilya Dryomov <[email protected]>

Author: Dan Carpenter

fs/ceph/inode.c

@@ -2492,7 +2492,7 @@ int ceph_getattr(struct user_namespace *mnt_userns, const struct path *path,
 			struct inode *parent;
 
 			parent = ceph_lookup_inode(sb, ceph_ino(inode));
-			if (!parent)
+			if (IS_ERR(parent))
 				return PTR_ERR(parent);
 
 			pci = ceph_inode(parent);