From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751990AbdAYKqK (ORCPT ); Wed, 25 Jan 2017 05:46:10 -0500 Received: from mx2.suse.de ([195.135.220.15]:55344 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751672AbdAYKqI (ORCPT ); Wed, 25 Jan 2017 05:46:08 -0500 Date: Wed, 25 Jan 2017 11:46:05 +0100 From: Michal Hocko To: Christoph Hellwig Cc: Tetsuo Handa , mgorman@suse.de, viro@ZenIV.linux.org.uk, linux-mm@kvack.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone Message-ID: <20170125104605.GI32377@dhcp22.suse.cz> References: <20170118172944.GA17135@dhcp22.suse.cz> <20170119100755.rs6erdiz5u5by2pu@suse.de> <20170119112336.GN30786@dhcp22.suse.cz> <20170119131143.2ze5l5fwheoqdpne@suse.de> <201701202227.GCC13598.OHJMSQFVOtFOLF@I-love.SAKURA.ne.jp> <201701211642.JBC39590.SFtVJHMFOLFOQO@I-love.SAKURA.ne.jp> <20170125101517.GG32377@dhcp22.suse.cz> <20170125101957.GA17632@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170125101957.GA17632@lst.de> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 25-01-17 11:19:57, Christoph Hellwig wrote: > On Wed, Jan 25, 2017 at 11:15:17AM +0100, Michal Hocko wrote: > > I think we are missing a check for fatal_signal_pending in > > iomap_file_buffered_write. This means that an oom victim can consume the > > full memory reserves. What do you think about the following? I haven't > > tested this but it mimics generic_perform_write so I guess it should > > work. > > Hi Michal, > > this looks reasonable to me. But we have a few more such loops, > maybe it makes sense to move the check into iomap_apply? I wasn't sure about the expected semantic of iomap_apply but now that I've actually checked all the callers I believe all of them should be able to handle EINTR just fine. Well iomap_file_dirty, iomap_zero_range, iomap_fiemap and iomap_page_mkwriteseem do not follow the standard pattern to return the number of written pages or an error but it rather propagates the error out. From my limited understanding of those code paths that should just be ok. I was not all that sure about iomap_dio_rw that is just too convoluted for me. If that one is OK as well then the following patch should be indeed better. --- >>From d99c9d4115bed69a5d71281f59c190b0b26627cf Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 25 Jan 2017 11:06:37 +0100 Subject: [PATCH] fs: break out of iomap_file_buffered_write on fatal signals Tetsuo has noticed that an OOM stress test which performs large write requests can cause the full memory reserves depletion. He has tracked this down to the following path __alloc_pages_nodemask+0x436/0x4d0 alloc_pages_current+0x97/0x1b0 __page_cache_alloc+0x15d/0x1a0 mm/filemap.c:728 pagecache_get_page+0x5a/0x2b0 mm/filemap.c:1331 grab_cache_page_write_begin+0x23/0x40 mm/filemap.c:2773 iomap_write_begin+0x50/0xd0 fs/iomap.c:118 iomap_write_actor+0xb5/0x1a0 fs/iomap.c:190 ? iomap_write_end+0x80/0x80 fs/iomap.c:150 iomap_apply+0xb3/0x130 fs/iomap.c:79 iomap_file_buffered_write+0x68/0xa0 fs/iomap.c:243 ? iomap_write_end+0x80/0x80 xfs_file_buffered_aio_write+0x132/0x390 [xfs] ? remove_wait_queue+0x59/0x60 xfs_file_write_iter+0x90/0x130 [xfs] __vfs_write+0xe5/0x140 vfs_write+0xc7/0x1f0 ? syscall_trace_enter+0x1d0/0x380 SyS_write+0x58/0xc0 do_syscall_64+0x6c/0x200 entry_SYSCALL64_slow_path+0x25/0x25 the oom victim has access to all memory reserves to make a forward progress to exit easier. But iomap_file_buffered_write and other callers of iomap_apply loop to complete the full request. We need to check for fatal signals and back off with a short write instead. Fixes: 68a9f5e7007c ("xfs: implement iomap based buffered write path") Cc: stable # 4.8+ Reported-by: Tetsuo Handa Signed-off-by: Michal Hocko --- fs/iomap.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/iomap.c b/fs/iomap.c index e57b90b5ff37..a58190f7a3e4 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -46,6 +46,9 @@ iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, struct iomap iomap = { 0 }; loff_t written = 0, ret; + if (fatal_signal_pending(current)) + return -EINTR; + /* * Need to map a range from start position for length bytes. This can * span multiple pages - it is only guaranteed to return a range of a -- 2.11.0 -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 8051E6B0069 for ; Wed, 25 Jan 2017 05:46:09 -0500 (EST) Received: by mail-wm0-f70.google.com with SMTP id r126so36189921wmr.2 for ; Wed, 25 Jan 2017 02:46:09 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 32si26303532wrx.326.2017.01.25.02.46.07 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 25 Jan 2017 02:46:07 -0800 (PST) Date: Wed, 25 Jan 2017 11:46:05 +0100 From: Michal Hocko Subject: Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone Message-ID: <20170125104605.GI32377@dhcp22.suse.cz> References: <20170118172944.GA17135@dhcp22.suse.cz> <20170119100755.rs6erdiz5u5by2pu@suse.de> <20170119112336.GN30786@dhcp22.suse.cz> <20170119131143.2ze5l5fwheoqdpne@suse.de> <201701202227.GCC13598.OHJMSQFVOtFOLF@I-love.SAKURA.ne.jp> <201701211642.JBC39590.SFtVJHMFOLFOQO@I-love.SAKURA.ne.jp> <20170125101517.GG32377@dhcp22.suse.cz> <20170125101957.GA17632@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170125101957.GA17632@lst.de> Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: Tetsuo Handa , mgorman@suse.de, viro@ZenIV.linux.org.uk, linux-mm@kvack.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org On Wed 25-01-17 11:19:57, Christoph Hellwig wrote: > On Wed, Jan 25, 2017 at 11:15:17AM +0100, Michal Hocko wrote: > > I think we are missing a check for fatal_signal_pending in > > iomap_file_buffered_write. This means that an oom victim can consume the > > full memory reserves. What do you think about the following? I haven't > > tested this but it mimics generic_perform_write so I guess it should > > work. > > Hi Michal, > > this looks reasonable to me. But we have a few more such loops, > maybe it makes sense to move the check into iomap_apply? I wasn't sure about the expected semantic of iomap_apply but now that I've actually checked all the callers I believe all of them should be able to handle EINTR just fine. Well iomap_file_dirty, iomap_zero_range, iomap_fiemap and iomap_page_mkwriteseem do not follow the standard pattern to return the number of written pages or an error but it rather propagates the error out. From my limited understanding of those code paths that should just be ok. I was not all that sure about iomap_dio_rw that is just too convoluted for me. If that one is OK as well then the following patch should be indeed better. ---