From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx113.postini.com [74.125.245.113]) by kanga.kvack.org (Postfix) with SMTP id 3E8F76B0002 for ; Tue, 5 Feb 2013 12:46:58 -0500 (EST) Received: by mail-we0-f182.google.com with SMTP id t57so377476wey.13 for ; Tue, 05 Feb 2013 09:46:56 -0800 (PST) Date: Tue, 5 Feb 2013 18:46:51 +0100 From: Michal Hocko Subject: Re: [PATCH for 3.2.34] memcg: do not trigger OOM from add_to_page_cache_locked Message-ID: <20130205174651.GA3959@dhcp22.suse.cz> References: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Greg Thelen Cc: azurIt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups mailinglist , KAMEZAWA Hiroyuki , Johannes Weiner On Tue 05-02-13 08:48:23, Greg Thelen wrote: > 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? I am not that familiar with VFS but i_mutex is a high level lock AFAIR and it shouldn't be called from the pageout path so __page_cache_alloc should be safe. -- 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