linux-kernel - Re: mm: kernel BUG at mm/huge

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Date:	Wed, 2 Dec 2015 08:41:48 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
CC:	Sasha Levin <sasha.levin@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: mm: kernel BUG at mm/huge_memory.c:3272!

On Tue, Dec 01, 2015 at 11:26:36PM +0200, Kirill A. Shutemov wrote:
> On Mon, Nov 30, 2015 at 09:37:33AM -0500, Sasha Levin wrote:
> > Hi Kirill,
> > 
> > I've hit the following while fuzzing with trinity on the latest -next kernel:
> > 
> > [  321.348184] page:ffffea0011a20080 count:1 mapcount:1 mapping:ffff8802d745f601 index:0x1802
> > [  321.350607] flags: 0x320035c00040078(uptodate|dirty|lru|active|swapbacked)
> > [  321.453706] page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
> > [  321.455353] page->mem_cgroup:ffff880286620000
> 
> I think this should help:
> 
> From aadc911f047b094c68b350550556dafabf05af13 Mon Sep 17 00:00:00 2001
> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Date: Fri, 20 Nov 2015 12:20:00 +0200
> Subject: [PATCH] thp: fix split_huge_page vs. deferred_split_scan race
> 
> Minchan[1] and Sasha[2] had reported crash in split_huge_page_to_list()
> called from deferred_split_scan() due VM_BUG_ON_PAGE(!PageLocked(page)).
> 
> This can happen because race between deferred_split_scan() and
> split_huge_page(). The result of the race is that the page can be split
> under deferred_split_scan().
> 
> The patch prevents this by taking split_queue_lock in
> split_huge_page_to_list() when we check if the page can be split.
> If the page is suitable for splitting, we remove page from splitting
> queue under the same lock, before splitting starts.
> 
> [1] http://lkml.kernel.org/g/20151117073539.GB32578@bbox
> [2] http://lkml.kernel.org/g/565C5F2D.5060003@oracle.com
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Reported-by: Minchan Kim <minchan@...nel.org>
> Reported-by: Sasha Levin <sasha.levin@...cle.com>

With this, I cannot reprocude the error.
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