From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f51.google.com (mail-wm0-f51.google.com [74.125.82.51]) by kanga.kvack.org (Postfix) with ESMTP id 0F9136B0005 for ; Thu, 25 Feb 2016 04:08:42 -0500 (EST) Received: by mail-wm0-f51.google.com with SMTP id g62so22760833wme.0 for ; Thu, 25 Feb 2016 01:08:42 -0800 (PST) Received: from mail-wm0-f65.google.com (mail-wm0-f65.google.com. [74.125.82.65]) by mx.google.com with ESMTPS id in5si8642117wjb.155.2016.02.25.01.08.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Feb 2016 01:08:41 -0800 (PST) Received: by mail-wm0-f65.google.com with SMTP id a4so2244479wme.3 for ; Thu, 25 Feb 2016 01:08:40 -0800 (PST) Date: Thu, 25 Feb 2016 10:08:39 +0100 From: Michal Hocko Subject: Re: [PATCH RFC] ext4: use __GFP_NOFAIL in ext4_free_blocks() Message-ID: <20160225090839.GC17573@dhcp22.suse.cz> References: <20160224170912.2195.8153.stgit@buzz> <56CEC2EC.5000506@kyup.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56CEC2EC.5000506@kyup.com> Sender: owner-linux-mm@kvack.org List-ID: To: Nikolay Borisov Cc: Konstantin Khlebnikov , Theodore Ts'o , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dmitry Monakhov , Johannes Weiner , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org On Thu 25-02-16 11:01:32, Nikolay Borisov wrote: > > > On 02/24/2016 07:09 PM, Konstantin Khlebnikov wrote: > > This might be unexpected but pages allocated for sbi->s_buddy_cache are > > charged to current memory cgroup. So, GFP_NOFS allocation could fail if > > current task has been killed by OOM or if current memory cgroup has no > > free memory left. Block allocator cannot handle such failures here yet. > > > > Signed-off-by: Konstantin Khlebnikov > > Adding new users of GFP_NOFAIL is deprecated. This is not true. GFP_NOFAIL should be used where the allocation failure is no tolleratable and it is much more preferrable to doing an opencoded endless loop over page allocator. > Where exactly does the > block allocator fail, I skimmed the code and failing ext4_mb_load_buddy > seems to be handled at all call sites. There are some BUG_ONs but from > the comments there I guess they should occur when we try to find a page > and not allocate a new one? I have posted a similar patch last year: http://lkml.kernel.org/r/1438768284-30927-6-git-send-email-mhocko@kernel.org because I could see emergency reboots when GFP_NOFS allocations were allowed to fail. -- Michal Hocko SUSE Labs -- 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