linux-ext4 - Re: [PATCH] ext4: page_cache pages not released in ext4_mb_load

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Date:	Fri, 26 Mar 2010 13:34:46 +0530
From:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	jing zhang <zj.barak@...il.com>
Cc:	linux-ext4 <linux-ext4@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>, Andreas Dilger <adilger@....com>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: Re: [PATCH] ext4: page_cache pages not released in
 ext4_mb_load_buddy()

On Thu, 25 Mar 2010 22:02:44 +0800, jing zhang <zj.barak@...il.com> wrote:
> 2010/3/25, Aneesh Kumar K. V <aneesh.kumar@...ux.vnet.ibm.com>:
> > On Wed, 24 Mar 2010 22:21:01 +0800, jing zhang <zj.barak@...il.com> wrote:
> >> From: Jing Zhang <zj.barak@...il.com>
> >>
> >> Date: Wed Mar 24 20:38:48     2010
> >>
> >> If ext4_mb_init_cache() returns error, there is no page_cache_release()
> >> issued.
> >>
> >> Cc: Theodore Ts'o <tytso@....edu>
> >> Cc: Andreas Dilger <adilger@....com>
> >> Cc: Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
> >> Signed-off-by: Jing Zhang <zj.barak@...il.com>
> >>
> >> ---
> >>
> >> --- linux-2.6.32/fs/ext4/mballoc.c	2009-12-03 11:51:22.000000000 +0800
> >> +++ ext4_mm_leak/mballoc-9.c	2010-03-24 22:24:56.000000000 +0800
> >> @@ -1132,8 +1132,6 @@ repeat_load_buddy:
> >>  	e4b->bd_buddy = page_address(page) + (poff * sb->s_blocksize);
> >>  	mark_page_accessed(page);
> >>
> >> -	BUG_ON(e4b->bd_bitmap_page == NULL);
> >> -	BUG_ON(e4b->bd_buddy_page == NULL);
> >
> > Why remove these ?
> 
> Just before return successfully, both bitmap page and buddy page are assigned.
> If not either, EIO will branch.
> 
> >
> >>
> >>  	return 0;
> >>
> >> @@ -1142,6 +1140,8 @@ err:
> >>  		page_cache_release(e4b->bd_bitmap_page);
> >>  	if (e4b->bd_buddy_page)
> >>  		page_cache_release(e4b->bd_buddy_page);
> >> +	if (page)
> >> +		page_cache_release(page);
> >>  	e4b->bd_buddy = NULL;
> >>  	e4b->bd_bitmap = NULL;
> >
> > Can you add a comment which says on error page will point to the page
> > cache page which haven't been assigned to neither bd_bitmap_page or
> > bd_buddy_page
> 
> +	if (page)
> +            /* we have to release page here in case that
> +             * ext4_mb_init_cache() returns error when preparing
> +             * either bitmap_ or buddy_page.
> +             */
> +		page_cache_release(page);
> 
> >
> > But good catch !!
> >
> > -aneesh
> >
> 
> Is that ok, Aneesh?

looks good

-aneesh
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