linux-kernel - Re: [PATCH 6/7] mm: add CONFIG_DEBUG_VM

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Date:	Fri, 21 Sep 2012 05:39:38 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Michel Lespinasse <walken@...gle.com>, linux-mm@...ck.org,
	riel@...hat.com, peterz@...radead.org, aarcange@...hat.com,
	hughd@...gle.com, daniel.santos@...ox.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Dave Jones <davej@...hat.com>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH 6/7] mm: add CONFIG_DEBUG_VM_RB build option

On Sat, Sep 15, 2012 at 11:26:23AM +0200, Sasha Levin wrote:
> On 09/15/2012 02:00 AM, Michel Lespinasse wrote:
> > All right. Hugh managed to reproduce the issue on his suse laptop, and
> > I came up with a fix.
> >
> > The problem was that in mremap, the new vma's vm_{start,end,pgoff}
> > fields need to be updated before calling anon_vma_clone() so that the
> > new vma will be properly indexed.
> >
> > Patch attached. I expect this should also explain Jiri's reported
> > failure involving splitting THP pages during mremap(), even though we
> > did not manage to reproduce that one.
>
> Initially I've stumbled on it by running trinity inside a KVM tools guest. fwiw,
> the guest is pretty custom and isn't based on suse.
>
> I re-ran tests with patch applied and looks like it fixed the issue, I haven't
> seen the warnings even though it runs for quite a while now.

Not sure if it's the same problem you are talking about, but I got the
below warning and it's still happening in linux-next 20120920:

[   38.482925] scsi_nl_rcv_msg: discarding partial skb
[   62.679879] ------------[ cut here ]------------
[   62.680380] WARNING: at /c/kernel-tests/src/linux/mm/interval_tree.c:109 anon_vma_interval_tree_verify+0x33/0x80()
[   62.681356] Pid: 195, comm: trinity-child0 Not tainted 3.6.0-rc6-next-20120918-08732-g3de9d1a #1
[   62.682130] Call Trace:
[   62.682356]  [<ffffffff810c249f>] ? anon_vma_interval_tree_verify+0x33/0x80
[   62.682968]  [<ffffffff81044356>] warn_slowpath_common+0x5d/0x74
[   62.683577]  [<ffffffff81044424>] warn_slowpath_null+0x15/0x19
[   62.684098]  [<ffffffff810c249f>] anon_vma_interval_tree_verify+0x33/0x80
[   62.684714]  [<ffffffff810ca57c>] validate_mm+0x32/0x15b
[   62.685202]  [<ffffffff810ca767>] vma_link+0x95/0xa4
[   62.685637]  [<ffffffff810cbc31>] copy_vma+0x1c7/0x1fe
[   62.686168]  [<ffffffff810cdd50>] move_vma+0x90/0x1ef
[   62.686614]  [<ffffffff810ce250>] sys_mremap+0x3a1/0x429
[   62.687094]  [<ffffffff813caafe>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[   62.687670]  [<ffffffff81b505b9>] system_call_fastpath+0x16/0x1b

Bisected down to 

commit cb58d445d2ec3a06f313e29d6f6af5bef6c9e43c
Author: Michel Lespinasse <walken@...gle.com>
Date:   Thu Sep 13 10:58:56 2012 +1000

    mm: add CONFIG_DEBUG_VM_RB build option

Thanks,
Fengguang

View attachment "dmesg-kvm-fat-3559-2012-09-19-10-31-29-3.6.0-rc6-next-20120918-08732-g3de9d1a-1" of type "text/plain" (165502 bytes)

View attachment "config-3.6.0-rc6-next-20120918-08732-g3de9d1a" of type "text/plain" (74858 bytes)