From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f44.google.com (mail-qa0-f44.google.com [209.85.216.44]) by kanga.kvack.org (Postfix) with ESMTP id 4922D6B0031 for ; Wed, 18 Dec 2013 23:16:24 -0500 (EST) Received: by mail-qa0-f44.google.com with SMTP id i13so4413443qae.3 for ; Wed, 18 Dec 2013 20:16:24 -0800 (PST) Received: from mail-vc0-x232.google.com (mail-vc0-x232.google.com [2607:f8b0:400c:c03::232]) by mx.google.com with ESMTPS id q18si1841673qeu.6.2013.12.18.20.16.23 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 18 Dec 2013 20:16:23 -0800 (PST) Received: by mail-vc0-f178.google.com with SMTP id lh4so340439vcb.37 for ; Wed, 18 Dec 2013 20:16:22 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1387424720-22826-1-git-send-email-liwanp@linux.vnet.ibm.com> References: <1387424720-22826-1-git-send-email-liwanp@linux.vnet.ibm.com> Date: Thu, 19 Dec 2013 12:16:22 +0800 Message-ID: Subject: Re: [PATCH v2] mm/rmap: fix BUG at rmap_walk From: Bob Liu Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: Andrew Morton , Sasha Levin , Hugh Dickins , Joonsoo Kim , Linux-MM , Linux-Kernel On Thu, Dec 19, 2013 at 11:45 AM, Wanpeng Li wrote: > page_get_anon_vma() called in page_referenced_anon() will lock and increase > the refcount of anon_vma, page won't be locked for anonymous page if the page > is not locked by the caller. This patch fix the BUG_ON by reuse referenced > field in page_referenced_arg to capture locked anonymous page for page_referenced(), > if the anonymous page is locked by the caller, the referenced field will remember > it, rmap_walk_anon will check if page locked if caller lock it. > Better commit log, please. This bug is introduced by commit 37f093cdf(mm/rmap: use rmap_walk() in page_referenced()). 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. > [ 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 | 20 ++++++++++++++++++-- > 2 files changed, 23 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..db83961 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -769,6 +769,10 @@ int page_referenced(struct page *page, > struct page_referenced_arg pra = { > .mapcount = page_mapcount(page), > .memcg = memcg, > + /* > + * reuse referenced field for the locked anonymous page check > + */ > + .referenced = is_locked && PageAnon(page) && !PageKsm(page), > }; > struct rmap_walk_control rwc = { > .rmap_one = page_referenced_one, > @@ -1587,6 +1591,12 @@ static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc) > pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); > struct anon_vma_chain *avc; > int ret = SWAP_AGAIN; > + struct page_referenced_arg *pra = rwc->arg; > + > + if (pra->referenced) { > + VM_BUG_ON(!PageLocked(page)); > + pra->referenced = 0; > + } > I don't this is needed. -- Regards, --Bob -- 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