From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f42.google.com (mail-wm0-f42.google.com [74.125.82.42]) by kanga.kvack.org (Postfix) with ESMTP id 415766B02F1 for ; Fri, 25 Dec 2015 06:35:41 -0500 (EST) Received: by mail-wm0-f42.google.com with SMTP id p187so201201137wmp.1 for ; Fri, 25 Dec 2015 03:35:41 -0800 (PST) Received: from mail-wm0-f49.google.com (mail-wm0-f49.google.com. [74.125.82.49]) by mx.google.com with ESMTPS id e196si63656088wmd.100.2015.12.25.03.35.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Dec 2015 03:35:39 -0800 (PST) Received: by mail-wm0-f49.google.com with SMTP id p187so198975634wmp.0 for ; Fri, 25 Dec 2015 03:35:39 -0800 (PST) Date: Fri, 25 Dec 2015 12:35:37 +0100 From: Michal Hocko Subject: Re: [PATCH 1/2] mm, oom: introduce oom reaper Message-ID: <20151225113537.GA6754@dhcp22.suse.cz> References: <1450204575-13052-1-git-send-email-mhocko@kernel.org> <20151224094758.GA22760@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: Ross Zwisler Cc: Andrew Morton , Mel Gorman , Tetsuo Handa , David Rientjes , Linus Torvalds , Oleg Nesterov , Hugh Dickins , Andrea Argangeli , Rik van Riel , linux-mm@kvack.org, LKML , Ross Zwisler On Thu 24-12-15 13:44:03, Ross Zwisler wrote: > On Thu, Dec 24, 2015 at 2:47 AM, Michal Hocko wrote: > > On Wed 23-12-15 16:00:09, Ross Zwisler wrote: > > [...] > >> While running xfstests on next-20151223 I hit a pair of kernel BUGs > >> that bisected to this commit: > >> > >> 1eb3a80d8239 ("mm, oom: introduce oom reaper") > > > > Thank you for the report and the bisection. > > > >> Here is a BUG produced by generic/029 when run against XFS: > >> > >> [ 235.751723] ------------[ cut here ]------------ > >> [ 235.752194] kernel BUG at mm/filemap.c:208! > > > > This is VM_BUG_ON_PAGE(page_mapped(page), page), right? Could you attach > > the full kernel log? It all smells like a race when OOM reaper tears > > down the mapping and there is a truncate still in progress. But hitting > > the BUG_ON just because of that doesn't make much sense to me. OOM > > reaper is essentially MADV_DONTNEED. I have to think about this some > > more, though, but I am in a holiday mode until early next year so please > > bear with me. > > The two stack traces were gathered with next-20151223, so the line numbers > may have moved around a bit when compared to the actual "mm, oom: introduce > oom reaper" commit. I was looking at the same next tree, I believe $ git describe next-20151223 [...] > > There was a warning before this triggered. The full kernel log would be > > helpful as well. > > Sure, I can gather full kernel logs, but it'll probably after the new year. OK, I will wait for the logs. It is really interesting to see what was the timing between OOM killer invocation and this trace. > > [...] > >> [ 609.425325] Call Trace: > >> [ 609.425797] [] invalidate_inode_pages2+0x17/0x20 > >> [ 609.426971] [] xfs_file_read_iter+0x297/0x300 > >> [ 609.428097] [] __vfs_read+0xc9/0x100 > >> [ 609.429073] [] vfs_read+0x89/0x130 > >> [ 609.430010] [] SyS_read+0x58/0xd0 > >> [ 609.430943] [] entry_SYSCALL_64_fastpath+0x12/0x76 > >> [ 609.432139] Code: 85 d8 fe ff ff 01 00 00 00 f6 c4 40 0f 84 59 ff > >> ff ff 49 8b 47 20 48 8d 78 ff a8 01 49 0f 44 ff 8b 47 48 85 c0 0f 88 > >> bd 01 00 00 <0f> 0b 4d 3b 67 08 0f 85 70 ff ff ff 49 f7 07 00 18 00 00 > >> 74 15 > > [...] > >> My test setup is a qemu guest machine with a pair of 4 GiB PMEM > >> ramdisk test devices, one for the xfstest test disk and one for the > >> scratch disk. > > > > Is this just a plain ramdisk device or it needs a special configuration? > > Just a plain PMEM ram disk with DAX turned off. Configuration instructions > for PMEM can be found here: > > https://nvdimm.wiki.kernel.org/ Thanks I will try to reproduce early next year. But so far I think this is just a general issue of MADV_DONTNEED vs. truncate and oom_reaper is just lucky to trigger it. There shouldn't be anything oom_reaper specific here. Maybe there is some additional locking missing? -- 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