From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752327AbaEUMJZ (ORCPT ); Wed, 21 May 2014 08:09:25 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43944 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751481AbaEUMJX (ORCPT ); Wed, 21 May 2014 08:09:23 -0400 Date: Wed, 21 May 2014 13:09:16 +0100 From: Mel Gorman To: Andrew Morton Cc: Johannes Weiner , Vlastimil Babka , Jan Kara , Michal Hocko , Hugh Dickins , Peter Zijlstra , Dave Hansen , Linux Kernel , Linux-MM , Linux-FSDevel , Prabhakar Lad Subject: Re: [PATCH] mm: non-atomically mark page accessed during page cache allocation where possible -fix Message-ID: <20140521120916.GS23991@suse.de> References: <1399974350-11089-1-git-send-email-mgorman@suse.de> <1399974350-11089-19-git-send-email-mgorman@suse.de> <20140520154900.GO23991@suse.de> <20140520123453.09a76dd0c8fad40082a16289@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20140520123453.09a76dd0c8fad40082a16289@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 20, 2014 at 12:34:53PM -0700, Andrew Morton wrote: > On Tue, 20 May 2014 16:49:00 +0100 Mel Gorman wrote: > > > Prabhakar Lad reported the following problem > > > > I see following issue on DA850 evm, > > git bisect points me to > > commit id: 975c3a671f11279441006a29a19f55ccc15fb320 > > ( mm: non-atomically mark page accessed during page cache allocation > > where possible) > > > > Unable to handle kernel paging request at virtual address 30e03501 > > pgd = c68cc000 > > [30e03501] *pgd=00000000 > > Internal error: Oops: 1 [#1] PREEMPT ARM > > Modules linked in: > > CPU: 0 PID: 1015 Comm: network.sh Not tainted 3.15.0-rc5-00323-g975c3a6 #9 > > task: c70c4e00 ti: c73d0000 task.ti: c73d0000 > > PC is at init_page_accessed+0xc/0x24 > > LR is at shmem_write_begin+0x54/0x60 > > pc : [] lr : [] psr: 20000013 > > sp : c73d1d90 ip : c73d1da0 fp : c73d1d9c > > r10: c73d1dec r9 : 00000000 r8 : 00000000 > > r7 : c73d1e6c r6 : c694d7bc r5 : ffffffe4 r4 : c73d1dec > > r3 : c73d0000 r2 : 00000001 r1 : 00000000 r0 : 30e03501 > > Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user > > Control: 0005317f Table: c68cc000 DAC: 00000015 > > Process network.sh (pid: 1015, stack limit = 0xc73d01c0) > > > > pagep is set but not pointing to anywhere valid as it's an uninitialised > > stack variable. This patch is a fix to > > mm-non-atomically-mark-page-accessed-during-page-cache-allocation-where-possible.patch > > > > ... > > > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -2459,7 +2459,7 @@ ssize_t generic_perform_write(struct file *file, > > flags |= AOP_FLAG_UNINTERRUPTIBLE; > > > > do { > > - struct page *page; > > + struct page *page = NULL; > > unsigned long offset; /* Offset into pagecache page */ > > unsigned long bytes; /* Bytes to write to page */ > > size_t copied; /* Bytes copied from user */ > > Well not really. generic_perform_write() only touches *page if > ->write_begin() returned "success", which is reasonable behavior. > > I'd say you mucked up shmem_write_begin() - it runs > init_page_accessed() even if shmem_getpage() returned an error. It > shouldn't be doing that. > > This? > > From: Andrew Morton > Subject: mm/shmem.c: don't run init_page_accessed() against an uninitialised pointer > > If shmem_getpage() returned an error then it didn't necessarily initialise > *pagep. So shmem_write_begin() shouldn't be playing with *pagep in this > situation. > > Fixes an oops when "mm: non-atomically mark page accessed during page > cache allocation where possible" (quite reasonably) left *pagep > uninitialized. > > Reported-by: Prabhakar Lad > Cc: Johannes Weiner > Cc: Vlastimil Babka > Cc: Jan Kara > Cc: Michal Hocko > Cc: Hugh Dickins > Cc: Peter Zijlstra > Cc: Dave Hansen > Cc: Mel Gorman > Signed-off-by: Andrew Morton Acked-by: Mel Gorman -- Mel Gorman SUSE Labs