From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f72.google.com (mail-it0-f72.google.com [209.85.214.72]) by kanga.kvack.org (Postfix) with ESMTP id 1DA2E6B0253 for ; Wed, 29 Nov 2017 08:44:54 -0500 (EST) Received: by mail-it0-f72.google.com with SMTP id p144so3002138itc.9 for ; Wed, 29 Nov 2017 05:44:54 -0800 (PST) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id a12si1388204ioc.14.2017.11.29.05.44.52 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 29 Nov 2017 05:44:52 -0800 (PST) Subject: Re: [PATCH v2 1/2] mm,vmscan: Make unregister_shrinker() no-op if register_shrinker() failed. From: Tetsuo Handa References: <20171124122148.qevmiogh3pzr4zix@dhcp22.suse.cz> <201711242221.BJD26077.SFOtVQJMFHOOFL@I-love.SAKURA.ne.jp> <20171124132857.vi4t7szmbknywng7@dhcp22.suse.cz> <201711251040.IHJ00547.FOFStVJOOMHFLQ@I-love.SAKURA.ne.jp> <20171127082936.27yt7sn2ucatvben@dhcp22.suse.cz> In-Reply-To: <20171127082936.27yt7sn2ucatvben@dhcp22.suse.cz> Message-Id: <201711292244.BHF26553.MOFQFtVJHOOFSL@I-love.SAKURA.ne.jp> Date: Wed, 29 Nov 2017 22:44:45 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org Cc: linux-mm@kvack.org, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, glauber@scylladb.com, syzkaller@googlegroups.com Michal Hocko wrote: > On Sat 25-11-17 10:40:13, Tetsuo Handa wrote: > > Michal Hocko wrote: > > > On Fri 24-11-17 22:21:55, Tetsuo Handa wrote: > > > > Michal Hocko wrote: > > > > > > Since we can encourage register_shrinker() callers to check for failure > > > > > > by marking register_shrinker() as __must_check, unregister_shrinker() > > > > > > can stay silent. > > > > > > > > > > I am not sure __must_check is the right way. We already do get > > > > > allocation warning if the registration fails so silent unregister is > > > > > acceptable. Unchecked register_shrinker is a bug like any other > > > > > unchecked error path. > > > > > > > > I consider that __must_check is the simplest way to find all of > > > > unchecked register_shrinker bugs. Why not to encourage users to fix? > > > > > > because git grep doesn't require to patch the kernel and still provide > > > the information you want. > > > > I can't interpret this line. How git grep relevant? > > you do not have to compile to see who is checking the return value. > Seriously there is no need to overcomplicate this. Newly added shrinkers > know the function returns might fail so we just have to handle existing > users and there are not all that many of those. Newly added shrinker users are not always careful. See commit f2517eb76f1f2f7f ("android: binder: Add global lru shrinker to binder") for example. Unless we send __must_check change to linux.git, people won't notice it. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org