linux-kernel - Re: [PATCH v3] mm/rmap: fix BUG at rmap

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Message-ID: <20131219055510.GA27532@lge.com>
Date:	Thu, 19 Dec 2013 14:55:10 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm/rmap: fix BUG at rmap_walk

On Thu, Dec 19, 2013 at 01:41:55PM +0800, Wanpeng Li wrote:
> 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:[<ffffffff81289c80>]  [<ffffffff81289c80>] 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]  [<ffffffff81289f4b>] page_referenced+0xcb/0x100
> [  588.707515]  [<ffffffff81289f80>] ? page_referenced+0x100/0x100
> [  588.707515]  [<ffffffff8128af60>] ? invalid_page_referenced_vma+0x170/0x170
> [  588.707515]  [<ffffffff81264302>] shrink_active_list+0x212/0x330
> [  588.707515]  [<ffffffff81260e23>] ? inactive_file_is_low+0x33/0x50
> [  588.707515]  [<ffffffff812646f5>] shrink_lruvec+0x2d5/0x300
> [  588.707515]  [<ffffffff812647b6>] shrink_zone+0x96/0x1e0
> [  588.707515]  [<ffffffff81265b06>] kswapd_shrink_zone+0xf6/0x1c0
> [  588.707515]  [<ffffffff81265f43>] balance_pgdat+0x373/0x550
> [  588.707515]  [<ffffffff81266d63>] kswapd+0x2f3/0x350
> [  588.707515]  [<ffffffff81266a70>] ? perf_trace_mm_vmscan_lru_isolate_template+0x120/0x120
> [  588.707515]  [<ffffffff8115c9c5>] kthread+0x105/0x110
> [  588.707515]  [<ffffffff8115c8c0>] ? set_kthreadd_affinity+0x30/0x30
> [  588.707515]  [<ffffffff843a6a7c>] ret_from_fork+0x7c/0xb0
> [  588.707515]  [<ffffffff8115c8c0>] ? 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  [<ffffffff81289c80>] rmap_walk+0x10/0x50
> [  588.707515]  RSP <ffff8800624518d8>
> 
> Reported-by: Sasha Levin <sasha.levin@...cle.com>
> Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>

Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Thanks for all relevant people. :)

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