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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7F413C432C1 for ; Tue, 24 Sep 2019 11:11:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59FA4214D9 for ; Tue, 24 Sep 2019 11:11:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440796AbfIXLLz (ORCPT ); Tue, 24 Sep 2019 07:11:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56368 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2395105AbfIXLLz (ORCPT ); Tue, 24 Sep 2019 07:11:55 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E43EF7FDCA; Tue, 24 Sep 2019 11:11:54 +0000 (UTC) Received: from localhost (ovpn-12-49.pek2.redhat.com [10.72.12.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4D92860603; Tue, 24 Sep 2019 11:11:53 +0000 (UTC) Date: Tue, 24 Sep 2019 19:11:51 +0800 From: Baoquan He To: akpm@linux-foundation.org, tj@kernel.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2] memcg: Only record foreign writebacks with dirty pages when memcg is not disabled Message-ID: <20190924111138.GA31919@MiWiFi-R3L-srv> References: <20190923083030.6442-1-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190923083030.6442-1-bhe@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 24 Sep 2019 11:11:55 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In kdump kernel, memcg usually is disabled with 'cgroup_disable=memory' for saving memory. Now kdump kernel will always panic when dump vmcore to local disk: BUG: kernel NULL pointer dereference, address: 0000000000000ab8 PGD 5fcab067 P4D 5fcab067 PUD 5ff73067 PMD 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 PID: 598 Comm: makedumpfile Not tainted 5.3.0+ #26 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 10/02/2018 RIP: 0010:mem_cgroup_track_foreign_dirty_slowpath+0x38/0x140 Code: 55 48 8b 2d 6a bd 12 01 53 4c 8b 67 38 0f 1f 44 00 00 49 8b 06 48 89 e9 31 db be ff ff ff ff 48 8b 38 49 8d 84 24 d0 0a 00 00 <48> 39 78 e8 74 5a 48 8b 50 f8 48 39 ca 79 0e 44 8b 00 41 83 f8 01 RSP: 0018:ffffbc9300817bd0 EFLAGS: 00010046 RAX: 0000000000000ad0 RBX: 0000000000000000 RCX: 00000000fffba227 RDX: fffffffffffffff8 RSI: 00000000ffffffff RDI: 0000000000000004 RBP: 00000000fffba227 R08: 0000000000030340 R09: ffffbc9300817d10 R10: 0000000000000000 R11: 0000000000001000 R12: 0000000000000000 R13: ffff999c1fa2bcf0 R14: ffff999c1f7bcc78 R15: ffffe51fc177a8c0 FS: 00007f84f14c2b80(0000) GS:ffff999c22200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000ab8 CR3: 000000005f564000 CR4: 00000000003406b0 Call Trace: __set_page_dirty+0x52/0xc0 iomap_set_page_dirty+0x50/0x90 iomap_write_end+0x6e/0x270 iomap_write_actor+0xce/0x170 ? iomap_write_end+0x270/0x270 iomap_apply+0xba/0x11e ? iomap_write_end+0x270/0x270 iomap_file_buffered_write+0x62/0x90 ? iomap_write_end+0x270/0x270 xfs_file_buffered_aio_write+0xca/0x320 [xfs] new_sync_write+0x12d/0x1d0 vfs_write+0xa5/0x1a0 ksys_write+0x59/0xd0 do_syscall_64+0x59/0x1e0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f84f1093ab5 And this will corrupt the 1st kernel too with 'cgroup_disable=memory'. >From the trace and with debugging, it is pointing to commit 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") which introduced this regression. Disabling memcg causes the null pointer dereference at uninitialized data in function mem_cgroup_track_foreign_dirty_slowpath(). Fix it by returning directly if memcg is disabled, but not trying to record the foreign writebacks with dirty pages. Fixed: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Baoquan He --- v1->v2: Move the checking code into mem_cgroup_track_foreign_dirty_slowpath() because usually memcg is enabled by default, and the original condition checking in mem_cgroup_track_foreign_dirty() is more unlikely being true to make it return. mm/memcontrol.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f3c15bb07cce..84e3fdb1ccb4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4317,6 +4317,9 @@ void mem_cgroup_track_foreign_dirty_slowpath(struct page *page, trace_track_foreign_dirty(page, wb); + if (mem_cgroup_disabled()) + return; + /* * Pick the slot to use. If there is already a slot for @wb, keep * using it. If not replace the oldest one which isn't being -- 2.17.2