From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757195Ab2IFKJb (ORCPT ); Thu, 6 Sep 2012 06:09:31 -0400 Received: from twin.jikos.cz ([89.185.236.188]:41299 "EHLO twin.jikos.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752837Ab2IFKJ3 (ORCPT ); Thu, 6 Sep 2012 06:09:29 -0400 Date: Thu, 6 Sep 2012 12:09:23 +0200 From: David Sterba To: Wang Sheng-Hui Cc: chris.mason@fusionio.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] btrfs: remove unnecessary -ENOMEM BUG_ON check in extent-tree.c/exclude_super_stripes Message-ID: <20120906100923.GO17430@twin.jikos.cz> Reply-To: dave@jikos.cz Mail-Followup-To: Wang Sheng-Hui , chris.mason@fusionio.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <50484569.8080709@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50484569.8080709@gmail.com> User-Agent: Mutt/1.5.21 (2011-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2012 at 02:40:41PM +0800, Wang Sheng-Hui wrote: > The memory allocation failure is BUG_ON in add_excluded_extent (following > the code path) and btrfs_rmap_block. No need to BUG_ON -ENOMEM inside > exclude_super_stripes itself. No please. > Its return value is always 0, and useless for its callers. Set it as void > instead 0-returned. btrfs_rmap_block itself contains a BUG_ON: 3980 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree, 3981 u64 chunk_start, u64 physical, u64 devid, 3982 u64 **logical, int *naddrs, int *stripe_len) 3983 { 3984 struct extent_map_tree *em_tree = &map_tree->map_tree; 3985 struct extent_map *em; 3986 struct map_lookup *map; 3987 u64 *buf; 3988 u64 bytenr; 3989 u64 length; 3990 u64 stripe_nr; 3991 int i, j, nr = 0; 3992 3993 read_lock(&em_tree->lock); 3994 em = lookup_extent_mapping(em_tree, chunk_start, 1); 3995 read_unlock(&em_tree->lock); 3996 3997 BUG_ON(!em || em->start != chunk_start); And this should be turned into an 'return error', thus giving a non-zero return code that should be handled in the callers. Eg. this patch attempts to do that http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg15470.html but has not been merged due to incorrect fix inside exclude_super_stripes (introduced in the patch). The same objection for return code cleanups will hold for any function that returns 0 but is full of BUG_ONs. david