From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f54.google.com (mail-oi0-f54.google.com [209.85.218.54]) by kanga.kvack.org (Postfix) with ESMTP id 668846B0038 for ; Tue, 9 Dec 2014 21:30:56 -0500 (EST) Received: by mail-oi0-f54.google.com with SMTP id u20so1374185oif.27 for ; Tue, 09 Dec 2014 18:30:56 -0800 (PST) Received: from userp1040.oracle.com (userp1040.oracle.com. [156.151.31.81]) by mx.google.com with ESMTPS id ts6si2015116obb.38.2014.12.09.18.30.52 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 09 Dec 2014 18:30:55 -0800 (PST) Message-ID: <5487AE8C.7000302@oracle.com> Date: Tue, 09 Dec 2014 21:23:08 -0500 From: Sasha Levin MIME-Version: 1.0 Subject: Re: mm: shmem: freeing mlocked page References: <545C4A36.9050702@oracle.com> <5466142C.60100@oracle.com> <20141118135843.bd711e95d3977c74cf51d803@linux-foundation.org> <5487ACC5.1010002@oracle.com> In-Reply-To: <5487ACC5.1010002@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Hugh Dickins , "linux-mm@kvack.org" , LKML , Dave Jones , Jens Axboe , Peter Zijlstra , Rik van Riel , Mel Gorman , dbueso@suse.de, kirill@shutemov.name (Apologies for spam, I've Cc'ed a few outdated emails in the previous mail) On 12/09/2014 09:15 PM, Sasha Levin wrote: > On 11/18/2014 04:58 PM, Andrew Morton wrote: >>> [ 1026.994816] Modules linked in: >>>> [ 1026.995378] CPU: 7 PID: 7879 Comm: trinity-c374 Not tainted 3.18.0-rc4-next-20141113-sasha-00047-gd1763ce-dirty #1455 >>>> [ 1026.996123] FAULT_INJECTION: forcing a failure. >>>> [ 1026.996123] name failslab, interval 100, probability 30, space 0, times -1 >>>> [ 1026.999050] 0000000000000000 0000000000000000 0000000000b3d300 ffff88061295bbd8 >>>> [ 1027.000676] ffffffff92f71097 0000000000000000 ffffea0000b3d300 ffff88061295bc08 >>>> [ 1027.002020] ffffffff8197ef7a ffffea0000b3d300 ffffffff942dd148 dfffe90000000000 >>>> [ 1027.003359] Call Trace: >>>> [ 1027.003831] dump_stack (lib/dump_stack.c:52) >>>> [ 1027.004725] bad_page (mm/page_alloc.c:338) >>>> [ 1027.005623] free_pages_prepare (mm/page_alloc.c:657 mm/page_alloc.c:763) >>>> [ 1027.006761] free_hot_cold_page (mm/page_alloc.c:1438) >>>> [ 1027.007772] ? __page_cache_release (mm/swap.c:66) >>>> [ 1027.008815] put_page (mm/swap.c:270) >>>> [ 1027.009665] page_cache_pipe_buf_release (fs/splice.c:93) >>>> [ 1027.010888] __splice_from_pipe (fs/splice.c:784 fs/splice.c:886) >>>> [ 1027.011917] ? might_fault (./arch/x86/include/asm/current.h:14 mm/memory.c:3734) >>>> [ 1027.012856] ? pipe_lock (fs/pipe.c:69) >>>> [ 1027.013728] ? write_pipe_buf (fs/splice.c:1534) >>>> [ 1027.014756] vmsplice_to_user (fs/splice.c:1574) >>>> [ 1027.015725] ? rcu_read_lock_held (kernel/rcu/update.c:169) >>>> [ 1027.016757] ? __fget_light (include/linux/fdtable.h:80 fs/file.c:684) >>>> [ 1027.017782] SyS_vmsplice (fs/splice.c:1656 fs/splice.c:1639) >>>> [ 1027.018863] tracesys_phase2 (arch/x86/kernel/entry_64.S:529) >>>> >> So what happened here? Userspace fed some mlocked memory into splice() >> and then, while splice() was running, userspace dropped its reference >> to the memory, leaving splice() with the last reference. Yet somehow, >> that page was still marked as being mlocked. I wouldn't expect the >> kernel to permit userspace to drop its reference to the memory without >> first clearing the mlocked state. >> >> Is it possible to work out from trinity sources what the exact sequence >> was? Which syscalls are being used, for example? > > Phew, this took a long while but I've bisected it (with good confidence) down > to: > > commit a38246260912ba4a0f8b563704a965a7a97cf3c3 > Author: Davidlohr Bueso > Date: Wed Dec 3 18:54:27 2014 +1100 > > mm/memory.c: share the i_mmap_rwsem > > The unmap_mapping_range family of functions do the unmapping of user pages > (ultimately via zap_page_range_single) without touching the actual > interval tree, thus share the lock. > > Signed-off-by: Davidlohr Bueso > Cc: "Kirill A. Shutemov" > Acked-by: Hugh Dickins > Cc: Oleg Nesterov > Cc: Peter Zijlstra (Intel) > Cc: Rik van Riel > Cc: Srikar Dronamraju > Acked-by: Mel Gorman > Signed-off-by: Andrew Morton > > > Thanks, > Sasha > -- 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