Re: list corruption in deferred_split_scan()

[Yang Shi <yang.shi@linux.alibaba.com>]

On 7/25/19 2:46 PM, Yang Shi wrote:
>
>
> On 7/24/19 2:13 PM, Qian Cai wrote:
>> On Wed, 2019-07-10 at 17:43 -0400, Qian Cai wrote:
>>> Running LTP oom01 test case with swap triggers a crash below. Revert 
>>> the
>>> series
>>> "Make deferred split shrinker memcg aware" [1] seems fix the issue.
>> You might want to look harder on this commit, as reverted it alone on 
>> the top of
>>   5.2.0-next-20190711 fixed the issue.
>>
>> aefde94195ca mm: thp: make deferred split shrinker memcg aware [1]
>>
>> [1] 
>> https://lore.kernel.org/linux-mm/1561507361-59349-5-git-send-email-yang.shi@
>> linux.alibaba.com/
>
> This is the real meat of the patch series, which converted to memcg 
> deferred split queue actually.
>
>>
>>
>> list_del corruption. prev->next should be ffffea0022b10098, but was
>> 0000000000000000
>
> Finally I could reproduce the list corruption issue on my machine with 
> THP swap (swap device is fast device). I should checked this with you 
> at the first place. The problem can't be reproduced with rotate swap 
> device. So, I'm supposed you were using THP swap too.
>
> Actually, I found two issues with THP swap:
> 1. free_transhuge_page() is called in reclaim path instead of 
> put_page. The mem_cgroup_uncharge() is called before 
> free_transhuge_page() in reclaim path, which causes page->mem_cgroup 
> is NULL so the wrong deferred_split_queue would be used, so the THP 
> was not deleted from the memcg's list at all. Then the page might be 
> split or reused later, page->mapping would be override.
>
> 2. There is a race condition caused by try_to_unmap() with THP swap. 
> The try_to_unmap() just calls page_remove_rmap() to add THP to 
> deferred split queue in reclaim path. This might cause the below race 
> condition to corrupt the list:
>
>                   A                                      B
> deferred_split_scan
>     list_move
>                                                try_to_unmap
> list_add_tail
>
> list_splice <-- The list might get corrupted here
>
>                                                free_transhuge_page
>                                                       list_del <-- 
> kernel bug triggered
>
> I hope the below patch would solve your problem (tested locally).

Hi Qian,

Did the below patch solve your problem? I would like the fold the fix 
into the series then target to 5.4 release.

Thanks,
Yang

>
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index b7f709d..d6612ec 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2830,6 +2830,19 @@ void deferred_split_huge_page(struct page *page)
>
>         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
>
> +       /*
> +        * The try_to_unmap() in page reclaim path might reach here too,
> +        * this may cause a race condition to corrupt deferred split 
> queue.
> +        * And, if page reclaim is already handling the same page, it is
> +        * unnecessary to handle it again in shrinker.
> +        *
> +        * Check PageSwapCache to determine if the page is being
> +        * handled by page reclaim since THP swap would add the page into
> +        * swap cache before reaching try_to_unmap().
> +        */
> +       if (PageSwapCache(page))
> +               return;
> +
>         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
>         if (list_empty(page_deferred_list(page))) {
>                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a0301ed..40c684a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1485,10 +1485,9 @@ static unsigned long shrink_page_list(struct 
> list_head *page_list,
>                  * Is there need to periodically free_page_list? It would
>                  * appear not as the counts should be low
>                  */
> -               if (unlikely(PageTransHuge(page))) {
> -                       mem_cgroup_uncharge(page);
> +               if (unlikely(PageTransHuge(page)))
>                         (*get_compound_page_dtor(page))(page);
> -               } else
> +               else
>                         list_add(&page->lru, &free_pages);
>                 continue;
>
> @@ -1909,7 +1908,6 @@ static unsigned noinline_for_stack 
> move_pages_to_lru(struct lruvec *lruvec,
>
>                         if (unlikely(PageCompound(page))) {
> spin_unlock_irq(&pgdat->lru_lock);
> -                               mem_cgroup_uncharge(page);
> (*get_compound_page_dtor(page))(page);
> spin_lock_irq(&pgdat->lru_lock);
>                         } else
>
>> [  685.284254][ T3456] ------------[ cut here ]------------
>> [  685.289616][ T3456] kernel BUG at lib/list_debug.c:53!
>> [  685.294808][ T3456] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC 
>> KASAN NOPTI
>> [  685.301998][ T3456] CPU: 5 PID: 3456 Comm: oom01 Tainted:
>> G        W         5.2.0-next-20190711+ #3
>> [  685.311193][ T3456] Hardware name: HPE ProLiant DL385 
>> Gen10/ProLiant DL385
>> Gen10, BIOS A40 06/24/2019
>> [  685.320485][ T3456] RIP: 0010:__list_del_entry_valid+0x8b/0xb6
>> [  685.326364][ T3456] Code: f1 e0 ff 49 8b 55 08 4c 39 e2 75 2c 5b 
>> b8 01 00 00
>> 00 41 5c 41 5d 5d c3 4c 89 e2 48 89 de 48 c7 c7 c0 5a 73 a3 e8 d9 fa 
>> bc ff <0f>
>> 0b 48 c7 c7 60 a0 e1 a3 e8 13 52 01 00 4c 89 e6 48 c7 c7 20 5b
>> [  685.345956][ T3456] RSP: 0018:ffff888e0c8a73c0 EFLAGS: 00010082
>> [  685.351920][ T3456] RAX: 0000000000000054 RBX: ffffea0022b10098 RCX:
>> ffffffffa2d5d708
>> [  685.359807][ T3456] RDX: 0000000000000000 RSI: 0000000000000008 RDI:
>> ffff8888442bd380
>> [  685.367693][ T3456] RBP: ffff888e0c8a73d8 R08: ffffed1108857a71 R09:
>> ffffed1108857a70
>> [  685.375577][ T3456] R10: ffffed1108857a70 R11: ffff8888442bd387 R12:
>> 0000000000000000
>> [  685.383462][ T3456] R13: 0000000000000000 R14: ffffea0022b10034 R15:
>> ffffea0022b10098
>> [  685.391348][ T3456] FS:  00007fbe26db4700(0000) 
>> GS:ffff888844280000(0000)
>> knlGS:0000000000000000
>> [  685.400194][ T3456] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [  685.406681][ T3456] CR2: 00007fbcabb3f000 CR3: 0000001012e44000 CR4:
>> 00000000001406a0
>> [  685.414563][ T3456] Call Trace:
>> [  685.417736][ T3456]  deferred_split_scan+0x337/0x740
>> [  685.422741][ T3456]  ? split_huge_page_to_list+0xe10/0xe10
>> [  685.428272][ T3456]  ? __radix_tree_lookup+0x12d/0x1e0
>> [  685.433453][ T3456]  ? node_tag_get.part.0.constprop.6+0x40/0x40
>> [  685.439505][ T3456]  do_shrink_slab+0x244/0x5a0
>> [  685.444071][ T3456]  shrink_slab+0x253/0x440
>> [  685.448375][ T3456]  ? unregister_shrinker+0x110/0x110
>> [  685.453551][ T3456]  ? kasan_check_read+0x11/0x20
>> [  685.458291][ T3456]  ? mem_cgroup_protected+0x20f/0x260
>> [  685.463555][ T3456]  shrink_node+0x31e/0xa30
>> [  685.467858][ T3456]  ? shrink_node_memcg+0x1560/0x1560
>> [  685.473036][ T3456]  ? ktime_get+0x93/0x110
>> [  685.477250][ T3456]  do_try_to_free_pages+0x22f/0x820
>> [  685.482338][ T3456]  ? shrink_node+0xa30/0xa30
>> [  685.486815][ T3456]  ? kasan_check_read+0x11/0x20
>> [  685.491556][ T3456]  ? check_chain_key+0x1df/0x2e0
>> [  685.496383][ T3456]  try_to_free_pages+0x242/0x4d0
>> [  685.501209][ T3456]  ? do_try_to_free_pages+0x820/0x820
>> [  685.506476][ T3456]  __alloc_pages_nodemask+0x9ce/0x1bc0
>> [  685.511826][ T3456]  ? gfp_pfmemalloc_allowed+0xc0/0xc0
>> [  685.517089][ T3456]  ? kasan_check_read+0x11/0x20
>> [  685.521826][ T3456]  ? check_chain_key+0x1df/0x2e0
>> [  685.526657][ T3456]  ? do_anonymous_page+0x343/0xe30
>> [  685.531658][ T3456]  ? lock_downgrade+0x390/0x390
>> [  685.536399][ T3456]  ? get_kernel_page+0xa0/0xa0
>> [  685.541050][ T3456]  ? __lru_cache_add+0x108/0x160
>> [  685.545879][ T3456]  alloc_pages_vma+0x89/0x2c0
>> [  685.550444][ T3456]  do_anonymous_page+0x3e1/0xe30
>> [  685.555271][ T3456]  ? __update_load_avg_cfs_rq+0x2c/0x490
>> [  685.560796][ T3456]  ? finish_fault+0x120/0x120
>> [  685.565361][ T3456]  ? alloc_pages_vma+0x21e/0x2c0
>> [  685.570187][ T3456]  handle_pte_fault+0x457/0x12c0
>> [  685.575014][ T3456]  __handle_mm_fault+0x79a/0xa50
>> [  685.579841][ T3456]  ? vmf_insert_mixed_mkwrite+0x20/0x20
>> [  685.585280][ T3456]  ? kasan_check_read+0x11/0x20
>> [  685.590021][ T3456]  ? __count_memcg_events+0x8b/0x1c0
>> [  685.595196][ T3456]  handle_mm_fault+0x17f/0x370
>> [  685.599850][ T3456]  __do_page_fault+0x25b/0x5d0
>> [  685.604501][ T3456]  do_page_fault+0x4c/0x2cf
>> [  685.608892][ T3456]  ? page_fault+0x5/0x20
>> [  685.613019][ T3456]  page_fault+0x1b/0x20
>> [  685.617058][ T3456] RIP: 0033:0x410be0
>> [  685.620840][ T3456] Code: 89 de e8 e3 23 ff ff 48 83 f8 ff 0f 84 
>> 86 00 00 00
>> 48 89 c5 41 83 fc 02 74 28 41 83 fc 03 74 62 e8 95 29 ff ff 31 d2 48 
>> 98 90 <c6>
>> 44 15 00 07 48 01 c2 48 39 d3 7f f3 31 c0 5b 5d 41 5c c3 0f 1f
>> [  68[  687.120156][ T3456] Shutting down cpus with NMI
>> [  687.124731][ T3456] Kernel Offset: 0x21800000 from 0xffffffff81000000
>> (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
>> [  687.136389][ T3456] ---[ end Kernel panic - not syncing: Fatal 
>> exception ]---
>