From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f181.google.com (mail-pd0-f181.google.com [209.85.192.181]) by kanga.kvack.org (Postfix) with ESMTP id 641DE6B0031 for ; Thu, 19 Dec 2013 00:42:11 -0500 (EST) Received: by mail-pd0-f181.google.com with SMTP id p10so650852pdj.40 for ; Wed, 18 Dec 2013 21:42:10 -0800 (PST) Received: from e23smtp08.au.ibm.com (e23smtp08.au.ibm.com. [202.81.31.141]) by mx.google.com with ESMTPS id zi8si1692826pac.243.2013.12.18.21.42.08 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 18 Dec 2013 21:42:09 -0800 (PST) Received: from /spool/local by e23smtp08.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 19 Dec 2013 15:42:04 +1000 Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 9BEAA3578050 for ; Thu, 19 Dec 2013 16:42:00 +1100 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id rBJ5flhp2687418 for ; Thu, 19 Dec 2013 16:41:48 +1100 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id rBJ5fxKH000600 for ; Thu, 19 Dec 2013 16:41:59 +1100 From: Wanpeng Li Subject: [PATCH v3] mm/rmap: fix BUG at rmap_walk Date: Thu, 19 Dec 2013 13:41:55 +0800 Message-Id: <1387431715-6786-1-git-send-email-liwanp@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Sasha Levin , Hugh Dickins , Joonsoo Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li This bug is introduced by commit 37f093cdf(mm/rmap: use rmap_walk() in page_referenced()). page_get_anon_vma() called in page_referenced_anon() will lock and increase the refcount of anon_vma. PageLocked is not required by page_referenced_anon() and there is not any assertion before, commit 37f093cdf introduced this extra BUG_ON() checking for anon page by mistake. This patch fix it by remove rmap_walk()'s VM_BUG_ON() and comment reason why the page must be locked for rmap_walk_ksm() and rmap_walk_file(). [ 588.698828] kernel BUG at mm/rmap.c:1663! [ 588.699380] invalid opcode: 0000 [#2] PREEMPT SMP DEBUG_PAGEALLOC [ 588.700347] Dumping ftrace buffer: [ 588.701186] (ftrace buffer empty) [ 588.702062] Modules linked in: [ 588.702759] CPU: 0 PID: 4647 Comm: kswapd0 Tainted: G D W 3.13.0-rc4-next-20131218-sasha-00012-g1962367-dirty #4155 [ 588.704330] task: ffff880062bcb000 ti: ffff880062450000 task.ti: ffff880062450000 [ 588.705507] RIP: 0010:[] [] rmap_walk+0x10/0x50 [ 588.706800] RSP: 0018:ffff8800624518d8 EFLAGS: 00010246 [ 588.707515] RAX: 000fffff80080048 RBX: ffffea00000227c0 RCX: 0000000000000000 [ 588.707515] RDX: 0000000000000000 RSI: ffff8800624518e8 RDI: ffffea00000227c0 [ 588.707515] RBP: ffff8800624518d8 R08: ffff8800624518e8 R09: 0000000000000000 [ 588.707515] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800624519d8 [ 588.707515] R13: 0000000000000000 R14: ffffea00000227e0 R15: 0000000000000000 [ 588.707515] FS: 0000000000000000(0000) GS:ffff880065200000(0000) knlGS:0000000000000000 [ 588.707515] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 588.707515] CR2: 00007fec40cbe0f8 CR3: 00000000c2382000 CR4: 00000000000006f0 [ 588.707515] Stack: [ 588.707515] ffff880062451958 ffffffff81289f4b ffff880062451918 ffffffff81289f80 [ 588.707515] 0000000000000000 0000000000000000 ffffffff8128af60 0000000000000000 [ 588.707515] 0000000000000024 0000000000000000 0000000000000000 0000000000000286 [ 588.707515] Call Trace: [ 588.707515] [] page_referenced+0xcb/0x100 [ 588.707515] [] ? page_referenced+0x100/0x100 [ 588.707515] [] ? invalid_page_referenced_vma+0x170/0x170 [ 588.707515] [] shrink_active_list+0x212/0x330 [ 588.707515] [] ? inactive_file_is_low+0x33/0x50 [ 588.707515] [] shrink_lruvec+0x2d5/0x300 [ 588.707515] [] shrink_zone+0x96/0x1e0 [ 588.707515] [] kswapd_shrink_zone+0xf6/0x1c0 [ 588.707515] [] balance_pgdat+0x373/0x550 [ 588.707515] [] kswapd+0x2f3/0x350 [ 588.707515] [] ? perf_trace_mm_vmscan_lru_isolate_template+0x120/0x120 [ 588.707515] [] kthread+0x105/0x110 [ 588.707515] [] ? set_kthreadd_affinity+0x30/0x30 [ 588.707515] [] ret_from_fork+0x7c/0xb0 [ 588.707515] [] ? set_kthreadd_affinity+0x30/0x30 [ 588.707515] Code: c0 48 83 c4 18 89 d0 5b 41 5c 41 5d 41 5e 41 5f c9 c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 66 66 66 66 90 48 8b 07 a8 01 75 10 <0f> 0b 66 0f 1f 44 00 0 0 eb fe 66 0f 1f 44 00 00 f6 47 08 01 74 [ 588.707515] RIP [] rmap_walk+0x10/0x50 [ 588.707515] RSP Reported-by: Sasha Levin Signed-off-by: Wanpeng Li --- mm/ksm.c | 5 +++++ mm/rmap.c | 10 ++++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index c9a28dd..76d96df 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1899,6 +1899,11 @@ int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc) int search_new_forks = 0; VM_BUG_ON(!PageKsm(page)); + + /* + * Rely on the page lock to protect against concurrent modifications + * to that page's node of the stable tree. + */ VM_BUG_ON(!PageLocked(page)); stable_node = page_stable_node(page); diff --git a/mm/rmap.c b/mm/rmap.c index d792e71..a0a199d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1629,6 +1629,14 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc) struct vm_area_struct *vma; int ret = SWAP_AGAIN; + /* + * The page lock not only makes sure that page->mapping cannot + * suddenly be NULLified by truncation, it makes sure that the + * structure at mapping cannot be freed and reused yet, + * so we can safely take mapping->i_mmap_mutex. + */ + VM_BUG_ON(!PageLocked(page)); + if (!mapping) return ret; mutex_lock(&mapping->i_mmap_mutex); @@ -1660,8 +1668,6 @@ done: int rmap_walk(struct page *page, struct rmap_walk_control *rwc) { - VM_BUG_ON(!PageLocked(page)); - if (unlikely(PageKsm(page))) return rmap_walk_ksm(page, rwc); else if (PageAnon(page)) -- 1.8.3.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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