From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx184.postini.com [74.125.245.184]) by kanga.kvack.org (Postfix) with SMTP id 1357E6B0008 for ; Tue, 5 Feb 2013 11:48:26 -0500 (EST) Received: by mail-ye0-f201.google.com with SMTP id r11so36027yen.4 for ; Tue, 05 Feb 2013 08:48:25 -0800 (PST) From: Greg Thelen Subject: Re: [PATCH for 3.2.34] memcg: do not trigger OOM from add_to_page_cache_locked References: <20121218152223.6912832C@pobox.sk> <20121218152004.GA25208@dhcp22.suse.cz> <20121224142526.020165D3@pobox.sk> <20121228162209.GA1455@dhcp22.suse.cz> <20121230020947.AA002F34@pobox.sk> <20121230110815.GA12940@dhcp22.suse.cz> <20130125160723.FAE73567@pobox.sk> <20130125163130.GF4721@dhcp22.suse.cz> <20130205134937.GA22804@dhcp22.suse.cz> <20130205154947.CD6411E2@pobox.sk> <20130205160934.GB22804@dhcp22.suse.cz> Date: Tue, 05 Feb 2013 08:48:23 -0800 In-Reply-To: <20130205160934.GB22804@dhcp22.suse.cz> (Michal Hocko's message of "Tue, 5 Feb 2013 17:09:34 +0100") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: azurIt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups mailinglist , KAMEZAWA Hiroyuki , Johannes Weiner On Tue, Feb 05 2013, Michal Hocko wrote: > On Tue 05-02-13 15:49:47, azurIt wrote: > [...] >> Just to be sure - am i supposed to apply this two patches? >> http://watchdog.sk/lkml/patches/ > > 5-memcg-fix-1.patch is not complete. It doesn't contain the folloup I > mentioned in a follow up email. Here is the full patch: > --- > From f2bf8437d5b9bb38a95a432bf39f32c584955171 Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Mon, 26 Nov 2012 11:47:57 +0100 > Subject: [PATCH] memcg: do not trigger OOM from add_to_page_cache_locked > > memcg oom killer might deadlock if the process which falls down to > mem_cgroup_handle_oom holds a lock which prevents other task to > terminate because it is blocked on the very same lock. > This can happen when a write system call needs to allocate a page but > the allocation hits the memcg hard limit and there is nothing to reclaim > (e.g. there is no swap or swap limit is hit as well and all cache pages > have been reclaimed already) and the process selected by memcg OOM > killer is blocked on i_mutex on the same inode (e.g. truncate it). > > Process A > [] do_truncate+0x58/0xa0 # takes i_mutex > [] do_last+0x250/0xa30 > [] path_openat+0xd7/0x440 > [] do_filp_open+0x49/0xa0 > [] do_sys_open+0x106/0x240 > [] sys_open+0x20/0x30 > [] system_call_fastpath+0x18/0x1d > [] 0xffffffffffffffff > > Process B > [] mem_cgroup_handle_oom+0x241/0x3b0 > [] T.1146+0x5ab/0x5c0 > [] mem_cgroup_cache_charge+0xbe/0xe0 > [] add_to_page_cache_locked+0x4c/0x140 > [] add_to_page_cache_lru+0x22/0x50 > [] grab_cache_page_write_begin+0x8b/0xe0 > [] ext3_write_begin+0x88/0x270 > [] generic_file_buffered_write+0x116/0x290 > [] __generic_file_aio_write+0x27c/0x480 > [] generic_file_aio_write+0x76/0xf0 # takes ->i_mutex > [] do_sync_write+0xea/0x130 > [] vfs_write+0xf3/0x1f0 > [] sys_write+0x51/0x90 > [] system_call_fastpath+0x18/0x1d > [] 0xffffffffffffffff It looks like grab_cache_page_write_begin() passes __GFP_FS into __page_cache_alloc() and mem_cgroup_cache_charge(). Which makes me think that this deadlock is also possible in the page allocator even before getting to add_to_page_cache_lru. no? Can callers holding fs resources (e.g. i_mutex) pass __GFP_FS into the page allocator? If __GFP_FS was avoided, then I think memcg user page charging would need a !__GFP_FS check to avoid invoking oom killer, but at least then we'd avoid both deadlocks and cover both page allocation and memcg page charging in similar fashion. Example from memcg_charge_kmem: may_oom = (gfp & __GFP_FS) && !(gfp & __GFP_NORETRY); -- 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