linux-kernel - Re: [BUG] 2.6.26-rc5-mm3 kernel BUG at mm/filemap.c:575!

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Message-Id: <20080613092520.fb35cd70.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 13 Jun 2008 09:25:20 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org,
	linux-mm@...ck.org, Nick Piggin <npiggin@...e.de>,
	Andy Whitcroft <apw@...dowen.org>
Subject: Re: [BUG] 2.6.26-rc5-mm3 kernel BUG at mm/filemap.c:575!

On Thu, 12 Jun 2008 21:38:59 +1000
Nick Piggin <nickpiggin@...oo.com.au> wrote:

> +int putback_lru_page(struct page *page)
> +{
> +       int lru;
> +       int ret = 1;
> +       int was_unevictable;
> +
> +       VM_BUG_ON(!PageLocked(page));
> +       VM_BUG_ON(PageLRU(page));
> +
> +       lru = !!TestClearPageActive(page);
> +       was_unevictable = TestClearPageUnevictable(page); /* for 
> page_evictable() */
> +
> +       if (unlikely(!page->mapping)) {
> +               /*
> +                * page truncated.  drop lock as put_page() will
> +                * free the page.
> +                */
> +               VM_BUG_ON(page_count(page) != 1);
> +               unlock_page(page);
>                 ^^^^^^^^^^^^^^^^^^
> 
> 
> This is a rather wild thing to be doing. It's a really bad idea
> to drop a lock that's taken several function calls distant and
> across different files...
> 
I agree and strongly hope this unlock should be removed.
The caller can do unlock by itself, I think.

Thanks,
-Kame

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