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Date:	Thu, 20 Mar 2014 17:21:09 +0800
From:	Bob Liu <bob.liu@...cle.com>
To:	Sasha Levin <sasha.levin@...cle.com>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: mm: kernel BUG at mm/swap.c:609!


On 03/12/2014 09:25 AM, Bob Liu wrote:
> 
> On 03/12/2014 04:07 AM, Sasha Levin wrote:
>> Hi all,
>>
>> While fuzzing with trinity inside a KVM tools guest running latest -next
>> kernel
>> I've stumbled on the following spew:
>>
>> [  477.301955] kernel BUG at mm/swap.c:609!
>> [  477.302564] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
>> [  477.303590] Dumping ftrace buffer:
>> [  477.305022]    (ftrace buffer empty)
>> [  477.305899] Modules linked in:
>> [  477.306397] CPU: 35 PID: 10092 Comm: trinity-c374 Tainted: G       
>> W    3.14.0-rc5-next-20140307-sasha-00010-g1f812cb #142
>> [  477.307644] task: ffff8800a7f80000 ti: ffff8800a7f6a000 task.ti:
>> ffff8800a7f6a000
>> [  477.309124] RIP: 0010:[<ffffffff8127f311>]  [<ffffffff8127f311>]
>> lru_cache_add+0x21/0x60
>> [  477.310301] RSP: 0000:ffff8800a7f6bbc8  EFLAGS: 00010292
>> [  477.311110] RAX: 000000000000003f RBX: ffffea0013d68000 RCX:
>> 0000000000000006
>> [  477.311110] RDX: 0000000000000006 RSI: ffff8800a7f80d60 RDI:
>> 0000000000000282
>> [  477.311110] RBP: ffff8800a7f6bbc8 R08: 0000000000000001 R09:
>> 0000000000000001
>> [  477.311110] R10: 0000000000000001 R11: 0000000000000001 R12:
>> ffff8800ab9b0c00
>> [  477.311110] R13: 0000000002400000 R14: ffff8800ab9b0c00 R15:
>> 0000000000000001
>> [  477.311110] FS:  00007ff2c047c700(0000) GS:ffff88042bc00000(0000)
>> knlGS:0000000000000000
>> [  477.311110] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>> [  477.311110] CR2: 0000000003788a68 CR3: 00000000a7f68000 CR4:
>> 00000000000006a0
>> [  477.311110] DR0: 000000000069b000 DR1: 0000000000000000 DR2:
>> 0000000000000000
>> [  477.311110] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
>> 0000000000000600
>> [  477.311110] Stack:
>> [  477.311110]  ffff8800a7f6bbf8 ffffffff812adaec ffffea0013d68000
>> ffffea002bdb8000
>> [  477.311110]  ffffea0013d68000 ffff8800a7f7c090 ffff8800a7f6bca8
>> ffffffff812db8ec
>> [  477.311110]  0000000000000001 ffffffff812e1321 ffff8800a7f6bc48
>> ffffffff811ad632
>> [  477.311110] Call Trace:
>> [  477.311110]  [<ffffffff812adaec>] page_add_new_anon_rmap+0x1ec/0x210
>> [  477.311110]  [<ffffffff812db8ec>]
>> migrate_misplaced_transhuge_page+0x55c/0x830
>> [  477.311110]  [<ffffffff812e1321>] ? do_huge_pmd_numa_page+0x311/0x460
>> [  477.311110]  [<ffffffff811ad632>] ? __lock_release+0x1e2/0x200
>> [  477.311110]  [<ffffffff812e133f>] do_huge_pmd_numa_page+0x32f/0x460
>> [  477.311110]  [<ffffffff81af6aca>] ? delay_tsc+0xfa/0x120
>> [  477.311110]  [<ffffffff812a31f4>] __handle_mm_fault+0x244/0x3a0
>> [  477.311110]  [<ffffffff812e37ed>] ? rcu_read_unlock+0x5d/0x60
>> [  477.311110]  [<ffffffff812a3463>] handle_mm_fault+0x113/0x1c0
>> [  477.311110]  [<ffffffff844abd42>] ? __do_page_fault+0x302/0x5d0
>> [  477.311110]  [<ffffffff844abfd1>] __do_page_fault+0x591/0x5d0
>> [  477.311110]  [<ffffffff8118ab46>] ? vtime_account_user+0x96/0xb0
>> [  477.311110]  [<ffffffff844ac492>] ? preempt_count_sub+0xe2/0x120
>> [  477.311110]  [<ffffffff81269567>] ?
>> context_tracking_user_exit+0x187/0x1d0
>> [  477.311110]  [<ffffffff844ac0d5>] do_page_fault+0x45/0x70
>> [  477.311110]  [<ffffffff844ab386>] do_async_page_fault+0x36/0x100
>> [  477.311110]  [<ffffffff844a7f18>] async_page_fault+0x28/0x30
>> [  477.311110] Code: 65 f0 4c 8b 6d f8 c9 c3 66 90 55 48 89 e5 66 66 66
>> 66 90 48 8b 07 a8 40 74 18 48 8b 07 a9 00 00 10 00 74 0e 31 f6 e8 2f 20
>> ff ff <0f> 0b eb fe 0f 1f 00 48 8b 07 a8 20 74 19 31 f6 e8 1a 20 ff ff
>> [  477.311110] RIP  [<ffffffff8127f311>] lru_cache_add+0x21/0x60
>> [  477.311110]  RSP <ffff8800a7f6bbc8>
>>
> 
> 
> If PageUnevictable(old_page) is true, new page will also be set before
> page_add_new_anon_rmap().
> 
> migrate_misplaced_transhuge_page()
>     > migrate_page_copy()
>         > SetPageUnevictable(newpage)
>     > page_add_new_anon_rmap()
> 
> But in page_add_new_anon_rmap(), there is only mlocked_vma_newpage()
> called to check whether a page should be added to unevictable list. I
> think that is incorrect in some cases and may trigger this BUG().
> 
> We can see from vmscan:
> int page_evictable(struct page *page)
> {
>     return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
> }
> 
> Besides mlock, we may also set a page to unevictable when that page's
> mapping marked unevictable.
> 
> mlocked_vma_newpage(new_page) can't detect this situation if the old
> page is set to unevictable by this reason. So I think we should add an
> extra !PageUnevictable(page) checking in page_add_new_anon_rmap().
> Fix me if I misunderstood something.
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 9056a1f..8d13318 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1024,7 +1024,7 @@ void page_add_new_anon_rmap(struct page *page,
>         __mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
>                         hpage_nr_pages(page));
>         __page_set_anon_rmap(page, vma, address, 1);
> -       if (!mlocked_vma_newpage(vma, page)) {
> +       if (!mlocked_vma_newpage(vma, page) && !PageUnevictable(page)) {
>                 SetPageActive(page);
>                 lru_cache_add(page);
>         } else
> 
> 

Sasha, any lucky with above changes? If it can fix this issue, I'll
resend out a patch.

-- 
Regards,
-Bob
--
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