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Message-ID: <20170411025615.GA6545@bbox>
Date: Tue, 11 Apr 2017 11:56:15 +0900
From: Minchan Kim <minchan@...nel.org>
To: alexander.levin@...izon.com
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"kernel-team@....com" <kernel-team@....com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v2 04/10] mm: make the try_to_munlock void function
Hi Sasha,
On Sat, Apr 08, 2017 at 03:18:35AM +0000, alexander.levin@...izon.com wrote:
> On Wed, Mar 15, 2017 at 02:24:47PM +0900, Minchan Kim wrote:
> > try_to_munlock returns SWAP_MLOCK if the one of VMAs mapped
> > the page has VM_LOCKED flag. In that time, VM set PG_mlocked to
> > the page if the page is not pte-mapped THP which cannot be
> > mlocked, either.
> >
> > With that, __munlock_isolated_page can use PageMlocked to check
> > whether try_to_munlock is successful or not without relying on
> > try_to_munlock's retval. It helps to make try_to_unmap/try_to_unmap_one
> > simple with upcoming patches.
> >
> > Cc: Vlastimil Babka <vbabka@...e.cz>
> > Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Signed-off-by: Minchan Kim <minchan@...nel.org>
>
> Hey Minchan,
>
> I seem to be hitting one of those newly added BUG_ONs with trinity:
>
> [ 21.017404] page:ffffea000307a300 count:10 mapcount:7 mapping:ffff88010083f3a8 index:0x131
> [ 21.019974] flags: 0x1fffc00001c001d(locked|referenced|uptodate|dirty|swapbacked|unevictable|mlocked) [ 21.022806] raw: 01fffc00001c001d ffff88010083f3a8 0000000000000131 0000000a00000006 [ 21.023974] raw: dead000000000100 dead000000000200 0000000000000000 ffff880109838008
> [ 21.026098] page dumped because: VM_BUG_ON_PAGE(PageMlocked(page))
> [ 21.026903] page->mem_cgroup:ffff880109838008 [ 21.027505] page allocated via order 0, migratetype Movable, gfp_mask 0x14200ca(GFP_HIGHUSER_MOVABLE)
> [ 21.028783] save_stack_trace (arch/x86/kernel/stacktrace.c:60)
> [ 21.029362] save_stack (./arch/x86/include/asm/current.h:14 mm/kasan/kasan.c:50) [ 21.029859] __set_page_owner (mm/page_owner.c:178) [ 21.030414] get_page_from_freelist (./include/linux/page_owner.h:30 mm/page_alloc.c:1742 mm/page_alloc.c:1750 mm/page_alloc.c:3097) [ 21.031071] __alloc_pages_nodemask (mm/page_alloc.c:4011) [ 21.031716] alloc_pages_vma (./include/linux/mempolicy.h:77 ./include/linux/mempolicy.h:82 mm/mempolicy.c:2024) [ 21.032307] shmem_alloc_page (mm/shmem.c:1389 mm/shmem.c:1444) [ 21.032881] shmem_getpage_gfp (mm/shmem.c:1474 mm/shmem.c:1753) [ 21.033488] shmem_fault (mm/shmem.c:1987) [ 21.034055] __do_fault (mm/memory.c:3012) [ 21.034568] __handle_mm_fault (mm/memory.c:3449 mm/memory.c:3497 mm/memory.c:3723 mm/memory.c:3841) [ 21.035192] handle_mm_fault (mm/memory.c:3878) [ 21.035772] __do_page_fault (arch/x86/mm/fault.c:1446) [ 21.037148] do_page_fault (arch/x86/mm/fault.c:1508 ./include/linux/context_tracking_state.h:30 ./include/linux/context_tracking.h:63 arch/x86/mm/fault.c:1509)
> [ 21.037657] do_async_page_fault (./arch/x86/include/asm/traps.h:82 arch/x86/kernel/kvm.c:264)
> [ 21.038266] async_page_fault (arch/x86/entry/entry_64.S:1011)
> [ 21.038901] ------------[ cut here ]------------
> [ 21.039546] kernel BUG at mm/rmap.c:1560!
> [ 21.040126] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
> [ 21.040910] Modules linked in:
> [ 21.041345] CPU: 6 PID: 1317 Comm: trinity-c62 Tainted: G W 4.11.0-rc5-next-20170407 #7
> [ 21.042761] task: ffff8801067d3e40 task.stack: ffff8800c06d0000
> [ 21.043572] RIP: 0010:try_to_munlock (??:?)
> [ 21.044639] RSP: 0018:ffff8800c06d71a0 EFLAGS: 00010296
> [ 21.045330] RAX: 0000000000000000 RBX: 1ffff100180dae36 RCX: 0000000000000000
> [ 21.046289] RDX: 0000000000000000 RSI: 0000000000000086 RDI: ffffed00180dae28
> [ 21.047225] RBP: ffff8800c06d7358 R08: 0000000000001639 R09: 6c7561665f656761
> [ 21.048982] R10: ffffea000307a31c R11: 303378302f383278 R12: ffff8800c06d7330
> [ 21.049823] R13: ffffea000307a300 R14: ffff8800c06d72d0 R15: ffffea000307a300
> [ 21.050647] FS: 00007f4ab05a7700(0000) GS:ffff880109d80000(0000) knlGS:0000000000000000
> [ 21.051574] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 21.052246] CR2: 00007f4aafdebfc0 CR3: 00000000c069f000 CR4: 00000000000406a0
> [ 21.053072] Call Trace:
> [ 21.061057] __munlock_isolated_page (mm/mlock.c:131)
> [ 21.065328] __munlock_pagevec (mm/mlock.c:339)
> [ 21.079191] munlock_vma_pages_range (mm/mlock.c:494)
> [ 21.085665] mlock_fixup (mm/mlock.c:569)
> [ 21.086205] apply_vma_lock_flags (mm/mlock.c:608)
> [ 21.089035] SyS_munlock (./arch/x86/include/asm/current.h:14 mm/mlock.c:739 mm/mlock.c:729)
> [ 21.089502] do_syscall_64 (arch/x86/entry/common.c:284)
>
Thanks for the report.
When I look at the code, that VM_BUG_ON check should be removed because
__munlock_pagevec doesn't hold any PG_lock so a page can have PG_mlocked
again before passing the page into try_to_munlock.
>From 4369227f190264291961bb4024e14d34e6656b54 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@...nel.org>
Date: Tue, 11 Apr 2017 11:41:54 +0900
Subject: [PATCH] mm: remove PG_Mlocked VM_BUG_ON check
Caller of try_to_munlock doesn't guarantee he pass the page
with clearing PG_mlocked.
Look at __munlock_pagevec which doesn't hold any PG_lock
so anybody can set PG_mlocked under us.
Remove bogus PageMlocked check in try_to_munlock.
Reported-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Minchan Kim <minchan@...nel.org>
---
Andrew,
This patch can be foled into mm-make-the-try_to_munlock-void-function.patch.
Thanks.
mm/rmap.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index a69a2a70d057..0773118214cc 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1557,7 +1557,6 @@ void try_to_munlock(struct page *page)
};
VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
- VM_BUG_ON_PAGE(PageMlocked(page), page);
VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
rmap_walk(page, &rwc);
--
2.7.4
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