Simplify exec_permission_lite(), part 3

Don't call down to the generic inode_permission() function just to
call the inode-specific permission function - just do it directly.

The generic inode_permission() code does things like checking MAY_WRITE
and devcgroup_inode_permission(), neither of which are relevant for the
light pathname walk permission checks (we always do just MAY_EXEC, and
the inode is never a special device).

Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -434,8 +434,12 @@ static int exec_permission_lite(struct inode *inode)
 {
 	umode_t	mode = inode->i_mode;
 
-	if (inode->i_op->permission)
-		return inode_permission(inode, MAY_EXEC);
+	if (inode->i_op->permission) {
+		int ret = inode->i_op->permission(inode, MAY_EXEC);
+		if (!ret)
+			goto ok;
+		return ret;
+	}
 
 	if (current_fsuid() == inode->i_uid)
 		mode >>= 6;