From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 665B1C282C4 for ; Mon, 4 Feb 2019 09:13:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 397F72147A for ; Mon, 4 Feb 2019 09:13:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728887AbfBDJNC (ORCPT ); Mon, 4 Feb 2019 04:13:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46876 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727958AbfBDJNC (ORCPT ); Mon, 4 Feb 2019 04:13:02 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DB89D81F13; Mon, 4 Feb 2019 09:13:01 +0000 (UTC) Received: from shodan.usersys.redhat.com (unknown [10.43.17.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 851EB7C0B3; Mon, 4 Feb 2019 09:13:01 +0000 (UTC) Received: by shodan.usersys.redhat.com (Postfix, from userid 1000) id CDA082C0AD2; Mon, 4 Feb 2019 10:13:00 +0100 (CET) Date: Mon, 4 Feb 2019 10:13:00 +0100 From: Artem Savkov To: Hugh Dickins Cc: Baoquan He , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: mm: race in put_and_wait_on_page_locked() Message-ID: <20190204091300.GB13536@shodan.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 04 Feb 2019 09:13:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Hugh, Your recent patch 9a1ea439b16b "mm: put_and_wait_on_page_locked() while page is migrated" seems to have introduced a race into page migration process. I have a host that eagerly reproduces the following BUG under stress: [ 302.847402] page:f000000000021700 count:0 mapcount:0 mapping:c0000000b2710bb0 index:0x19 [ 302.848096] xfs_address_space_operations [xfs] [ 302.848100] name:"libc-2.28.so" [ 302.848244] flags: 0x3ffff800000006(referenced|uptodate) [ 302.848521] raw: 003ffff800000006 5deadbeef0000100 5deadbeef0000200 0000000000000000 [ 302.848724] raw: 0000000000000019 0000000000000000 00000001ffffffff c0000000bc0b1000 [ 302.848919] page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0) [ 302.849076] page->mem_cgroup:c0000000bc0b1000 [ 302.849269] ------------[ cut here ]------------ [ 302.849397] kernel BUG at include/linux/mm.h:546! [ 302.849586] Oops: Exception in kernel mode, sig: 5 [#1] [ 302.849711] LE SMP NR_CPUS=2048 NUMA pSeries [ 302.849839] Modules linked in: pseries_rng sunrpc xts vmx_crypto virtio_balloon xfs libcrc32c virtio_net net_failover virtio_console failover virtio_blk [ 302.850400] CPU: 3 PID: 8759 Comm: cc1 Not tainted 5.0.0-rc4+ #36 [ 302.850571] NIP: c00000000039c8b8 LR: c00000000039c8b4 CTR: c00000000080a0e0 [ 302.850758] REGS: c0000000b0d7f7e0 TRAP: 0700 Not tainted (5.0.0-rc4+) [ 302.850952] MSR: 8000000000029033 CR: 48024422 XER: 00000000 [ 302.851150] CFAR: c0000000003ff584 IRQMASK: 0 [ 302.851150] GPR00: c00000000039c8b4 c0000000b0d7fa70 c000000001bcca00 0000000000000021 [ 302.851150] GPR04: c0000000b044c628 0000000000000007 55555555555555a0 c000000001fc3760 [ 302.851150] GPR08: 0000000000000007 0000000000000000 c0000000b0d7c000 c0000000b0d7f5ff [ 302.851150] GPR12: 0000000000004400 c00000003fffae80 0000000000000000 0000000000000000 [ 302.851150] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 [ 302.851150] GPR20: c0000000689f5aa8 c00000002a13ee48 0000000000000000 c000000001da29b0 [ 302.851150] GPR24: c000000001bf7d80 c0000000689f5a00 0000000000000000 0000000000000000 [ 302.851150] GPR28: c000000001bf9e80 c0000000b0d7fab8 0000000000000001 f000000000021700 [ 302.852914] NIP [c00000000039c8b8] put_and_wait_on_page_locked+0x398/0x3d0 [ 302.853080] LR [c00000000039c8b4] put_and_wait_on_page_locked+0x394/0x3d0 [ 302.853235] Call Trace: [ 302.853305] [c0000000b0d7fa70] [c00000000039c8b4] put_and_wait_on_page_locked+0x394/0x3d0 (unreliable) [ 302.853540] [c0000000b0d7fb10] [c00000000047b838] __migration_entry_wait+0x178/0x250 [ 302.853738] [c0000000b0d7fb50] [c00000000040c928] do_swap_page+0xd78/0xf60 [ 302.853997] [c0000000b0d7fbd0] [c000000000411078] __handle_mm_fault+0xbf8/0xe80 [ 302.854187] [c0000000b0d7fcb0] [c000000000411548] handle_mm_fault+0x248/0x450 [ 302.854379] [c0000000b0d7fd00] [c000000000078ca4] __do_page_fault+0x2d4/0xdf0 [ 302.854877] [c0000000b0d7fde0] [c0000000000797f8] do_page_fault+0x38/0xf0 [ 302.855057] [c0000000b0d7fe20] [c00000000000a7c4] handle_page_fault+0x18/0x38 [ 302.855300] Instruction dump: [ 302.855432] 4bfffcf0 60000000 3948ffff 4bfffd20 60000000 60000000 3c82ff36 7fe3fb78 [ 302.855689] fb210068 38843b78 48062f09 60000000 <0fe00000> 60000000 3b400001 3b600001 [ 302.855950] ---[ end trace a52140e0f9751ae0 ]--- What seems to be happening is migrate_page_move_mapping() calling page_ref_freeze() on another cpu somewhere between __migration_entry_wait() taking a reference and wait_on_page_bit_common() calling page_put(). -- Artem