Re: [PATCH -mm] mm,numa,mprotect: always continue after finding a stable thp page

[Davidlohr Bueso <davidlohr@hp.com>]

On Tue, 2014-03-11 at 18:06 +0000, Mel Gorman wrote:
> On Tue, Mar 11, 2014 at 01:33:00PM -0400, Sasha Levin wrote:
> > Okay. So just this patch on top of the latest -next shows the following issues:
> > 
> > 1. BUG in task_numa_work:
> > 
> > [  439.417171] BUG: unable to handle kernel paging request at ffff880e17530c00
> > [  439.418216] IP: [<ffffffff81299385>] vmacache_find+0x75/0xa0
> > [  439.419073] PGD 8904067 PUD 1028fcb067 PMD 1028f10067 PTE 8000000e17530060
> > [  439.420340] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> > [  439.420340] Dumping ftrace buffer:
> > [  439.420340]    (ftrace buffer empty)
> > [  439.420340] Modules linked in:
> > [  439.420340] CPU: 12 PID: 9937 Comm: trinity-c212 Tainted: G        W    3.14.0-rc5-next-20140307-sasha-00009-g3b24300-dirty #137
> > [  439.420340] task: ffff880e1a45b000 ti: ffff880e1a490000 task.ti: ffff880e1a490000
> > [  439.420340] RIP: 0010:[<ffffffff81299385>]  [<ffffffff81299385>] vmacache_find+0x75/0xa0
> > [  439.420340] RSP: 0018:ffff880e1a491e68  EFLAGS: 00010286
> > [  439.420340] RAX: ffff880e17530c00 RBX: 0000000000000000 RCX: 0000000000000001
> > [  439.420340] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff880e1a45b000
> > [  439.420340] RBP: ffff880e1a491e68 R08: 0000000000000000 R09: 0000000000000000
> > [  439.420340] R10: 0000000000000001 R11: 0000000000000000 R12: ffff880e1ab75000
> > [  439.420340] R13: ffff880e1ab75000 R14: 0000000000010000 R15: 0000000000000000
> > [  439.420340] FS:  00007f3458c05700(0000) GS:ffff880d2b800000(0000) knlGS:0000000000000000
> > [  439.420340] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > [  439.420340] CR2: ffff880e17530c00 CR3: 0000000e1a472000 CR4: 00000000000006a0
> > [  439.420340] Stack:
> > [  439.420340]  ffff880e1a491e98 ffffffff812a7610 ffffffff8118de40 0000000000000117
> > [  439.420340]  00000001000036da ffff880e1a45b000 ffff880e1a491ef8 ffffffff8118de4b
> > [  439.420340]  ffff880e1a491ec8 ffffffff81269575 ffff880e1ab750a8 ffff880e1a45b000
> > [  439.420340] Call Trace:
> > [  439.420340]  [<ffffffff812a7610>] find_vma+0x20/0x90
> > [  439.420340]  [<ffffffff8118de40>] ? task_numa_work+0x130/0x360
> > [  439.420340]  [<ffffffff8118de4b>] task_numa_work+0x13b/0x360
> > [  439.420340]  [<ffffffff81269575>] ? context_tracking_user_exit+0x195/0x1d0
> > [  439.420340]  [<ffffffff8116c5be>] task_work_run+0xae/0xf0
> > [  439.420340]  [<ffffffff8106ffbe>] do_notify_resume+0x8e/0xe0
> > [  439.420340]  [<ffffffff844b17a2>] int_signal+0x12/0x17
> > [  439.420340] Code: 42 10 00 00 00 00 48 c7 42 18 00 00 00 00 eb 38 66 0f 1f 44 00 00 31 d2 48 89 c7 48 63 ca 48 8b 84 cf b8 07 00 00 48 85 c0 74 0b <48> 39 30 77 06 48 3b 70 08 72 12 ff c2 83 fa 04 75 de 66 0f 1f
> > [  439.420340] RIP  [<ffffffff81299385>] vmacache_find+0x75/0xa0
> > [  439.420340]  RSP <ffff880e1a491e68>
> > [  439.420340] CR2: ffff880e17530c00
> > 
> 
> Ok, this does not look related. It looks like damage from the VMA caching
> patches, possibly a use-after free. I'm skeptical that it's related to
> automatic NUMA balancing as such based on the second trace you posted.

Indeed, this issue is separate. It was reported a few days ago by
Fengguang: http://lkml.org/lkml/2014/3/9/201

Apparently this has only been seen in DEBUG_PAGEALLOC + trinity
scenarios, just like in Sasha's trace. I'm suspecting some invalidation
is missing (not sure what DEBUG_PAGEALLOC enables differently in this
aspect), as when we do the vmacache_find() the vma is bogus which
triggers the paging request error.

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