linux-kernel - Re: [mmotm] BUG: Bad page state in process khugepaged ?

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Message-Id: <20110209155246.69a7f3a1.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 9 Feb 2011 15:52:46 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"hannes@...xchg.org" <hannes@...xchg.org>
Subject: Re: [mmotm] BUG: Bad page state in process khugepaged ?

On Wed, 9 Feb 2011 15:50:01 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> > 
> > In hex, pc->flags was 7A00000000004 and this means PCG_USED bit is set.
> > This implies page_remove_rmap() may not be called but ->mapping is NULL. Hmm?
> > (7A is encoding of section number.)
> > 
> Sigh.. it seems another freed-but-not-uncharged problem..
> 

Ah, ok, this is maybe caused by this. I'm sorry that I missed this.
==
static inline int free_pages_check(struct page *page)
{
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (atomic_read(&page->_count) != 0) |
                (page->flags & PAGE_FLAGS_CHECK_AT_FREE) |
                (mem_cgroup_bad_page_check(page)))) {    <==========(*)
                bad_page(page);
                return 1;
==

Then, ok, this is a memcgroup and hugepage issue.

I'll look into.

Thanks,
-Kame

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