On 2019/10/29 0:15, David Hildenbrand wrote: > On 28.10.19 17:07, David Hildenbrand wrote: >> On 28.10.19 16:45, zhong jiang wrote: >>> On 2019/10/28 23:27, David Hildenbrand wrote: >>>> On 28.10.19 16:08, zhong jiang wrote: >>>>> Recently, I hit the following issue when running in the upstream. >>>>> >>>>> kernel BUG at mm/vmscan.c:1521! >>>>> invalid opcode: 0000 [#1] SMP KASAN PTI >>>>> CPU: 0 PID: 23385 Comm: syz-executor.6 Not tainted 5.4.0-rc4+ #1 >>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 >>>>> RIP: 0010:shrink_page_list+0x12b6/0x3530 mm/vmscan.c:1521 >>>>> Code: de f5 ff ff e8 ab 79 eb ff 4c 89 f7 e8 43 33 0d 00 e9 cc f5 ff ff e8 99 79 eb ff 48 c7 c6 a0 34 2b a0 4c 89 f7 e8 1a 4d 05 00 <0f> 0b e8 83 79 eb ff 48 89 d8 48 c1 e8 03 42 80 3c 38 00 0f 85 74 >>>>> RSP: 0018:ffff88819a3df5a0 EFLAGS: 00010286 >>>>> RAX: 0000000000040000 RBX: ffffea00061c3980 RCX: ffffffff814fba36 >>>>> RDX: 00000000000056f7 RSI: ffffc9000c02c000 RDI: ffff8881f70268cc >>>>> RBP: ffff88819a3df898 R08: ffffed103ee05de0 R09: ffffed103ee05de0 >>>>> R10: 0000000000000001 R11: ffffed103ee05ddf R12: ffff88819a3df6f0 >>>>> R13: ffff88819a3df6f0 R14: ffffea00061c3980 R15: dffffc0000000000 >>>>> FS: 00007f21b9d8e700(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 >>>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>>> CR2: 0000001b2d621000 CR3: 00000001c8c46004 CR4: 00000000007606f0 >>>>> DR0: 0000000020000140 DR1: 0000000000000000 DR2: 0000000000000000 >>>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 >>>>> PKRU: 55555554 >>>>> Call Trace: >>>>> reclaim_pages+0x499/0x800 mm/vmscan.c:2188 >>>>> madvise_cold_or_pageout_pte_range+0x58a/0x710 mm/madvise.c:453 >>>>> walk_pmd_range mm/pagewalk.c:53 [inline] >>>>> walk_pud_range mm/pagewalk.c:112 [inline] >>>>> walk_p4d_range mm/pagewalk.c:139 [inline] >>>>> walk_pgd_range mm/pagewalk.c:166 [inline] >>>>> __walk_page_range+0x45a/0xc20 mm/pagewalk.c:261 >>>>> walk_page_range+0x179/0x310 mm/pagewalk.c:349 >>>>> madvise_pageout_page_range mm/madvise.c:506 [inline] >>>>> madvise_pageout+0x1f0/0x330 mm/madvise.c:542 >>>>> madvise_vma mm/madvise.c:931 [inline] >>>>> __do_sys_madvise+0x7d2/0x1600 mm/madvise.c:1113 >>>>> do_syscall_64+0x9f/0x4c0 arch/x86/entry/common.c:290 >>>>> entry_SYSCALL_64_after_hwframe+0x49/0xbe >>>>> >>>>> madvise_pageout access the specified range of the vma and isolate >>>>> them, then run shrink_page_list to reclaim the memory. But It also >>>>> isolate the unevictable page to reclaim. Hence, we can catch the >>>>> cases in shrink_page_list. >>>>> >>>>> We can fix it by preventing unevictable page from isolating. >>>>> Another way to fix the issue by removing the condition of >>>>> BUG_ON(PageUnevictable(page)) in shrink_page_list. I think it >>>>> is better to use the latter. Because We has taken the unevictable >>>>> page and skip it into account in shrink_page_list. >>>> I really don't understand the last sentence. Looks like >>>> something got messed up :) >>> I mean that we will check the page_evictable(page) in shrink_page_list, >>> if it is unevictable page, we will put the page back to correct lru. >>> >>> Based on the condition, I make the choice. It seems to more simpler.:-) >>> >>> Thanks, >>> zhong jiang >>>> >>>>> Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx> >>>>> --- >>>>> mm/vmscan.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>>>> index f7d1301..1c6e959 100644 >>>>> --- a/mm/vmscan.c >>>>> +++ b/mm/vmscan.c >>>>> @@ -1524,7 +1524,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, >>>>> unlock_page(page); >>>>> keep: >>>>> list_add(&page->lru, &ret_pages); >>>>> - VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page); >>>>> + VM_BUG_ON_PAGE(PageLRU(page), page); >>>> So, this comes from >>>> >>>> commit b291f000393f5a0b679012b39d79fbc85c018233 >>>> Author: Nick Piggin <npiggin@xxxxxxx> >>>> Date: Sat Oct 18 20:26:44 2008 -0700 >>>> >>>> mlock: mlocked pages are unevictable >>>> Make sure that mlocked pages also live on the unevictable LRU, so kswapd >>>> will not scan them over and over again. >>>> >>>> >>>> That patch is fairly old. How come we can suddenly trigger this? >>>> Which commit is responsible for that? Was it always broken? >>>> >>>> I can see that >>>> >>>> commit ad6b67041a45497261617d7a28b15159b202cb5a >>>> Author: Minchan Kim <minchan@xxxxxxxxxx> >>>> Date: Wed May 3 14:54:13 2017 -0700 >>>> >>>> mm: remove SWAP_MLOCK in ttu >>>> >>>> Performed some changes in that area. But also some time ago. >>> I think the following patch introduce the issue. >>> >>> commit 1a4e58cce84ee88129d5d49c064bd2852b481357 >>> Author: Minchan Kim <minchan@xxxxxxxxxx> >>> Date: Wed Sep 25 16:49:15 2019 -0700 >>> >>> mm: introduce MADV_PAGEOUT >>> >>> When a process expects no accesses to a certain memory range for a long >>> >> >> CCing Minchan Kim then. >> >> If this is indeed the introducing patch, you probably reference that >> patch in your cover mail somehow. (Fixes: does not apply until upstream) >> >> I am absolutely no expert on vmscan.c, so I'm afraid I can't really >> comment on the details. >> > > Oh, and just wondering, is this the same BUG as in > > https://lkml.org/lkml/2019/8/2/1506 > > Where a fix has been proposed? The fix does not seem to be in next/master yet. > > (I just realized that it is already upstream so "Fixes: 1a4e58cce84e ("mm: introduce MADV_PAGEOUT")) applies. > > > I think that is not same issue. thannks
