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

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Date:	Thu, 25 Mar 2010 22:02:44 +0800
From:	jing zhang <zj.barak@...il.com>
To:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.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()

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?

        - zj
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