linux-ext4 - Re: [PATCH] ext4: page_cache pages over pinned in ext4_mb_free

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Date:	Thu, 25 Mar 2010 22:23:42 +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 over pinned in 
	ext4_mb_free_metadata()

2010/3/25, Aneesh Kumar K. V <aneesh.kumar@...ux.vnet.ibm.com>:
> On Wed, 24 Mar 2010 21:00:34 +0800, jing zhang <zj.barak@...il.com> wrote:
>> From: Jing Zhang <zj.barak@...il.com>
>>
>> Date: Wed Mar 24 20:38:48     2010
>>
>> The function, ext4_mb_free_metadata(), is called after
>>      ext4_mb_load_buddy(sb, block_group, &e4b);
>> and before
>>      ext4_mb_release_desc(&e4b);
>> in the function, ext4_mb_free_blocks(), so the bd_bitmap_page and
>> bd_buddy_page of e4b are well managed.
>>
>> If for special purpose, page_cache_get() is issued on these two pages,
>> there should also be page_cache_release() issued correspondingly, or
>> the two pages are over pinned.
>
> release_blocks_on_commit does that. I also have a comment around that
> page_cache_release.

Thank you, Aneesh. I will check it.

      - zj

>
>>
>> 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/mballoc6.c	2010-03-24 20:31:52.000000000 +0800
>> @@ -4361,15 +4361,6 @@ ext4_mb_free_metadata(handle_t *handle,
>>  	new_node = &new_entry->node;
>>  	block = new_entry->start_blk;
>>
>> -	if (!*n) {
>> -		/* first free block exent. We need to
>> -		   protect buddy cache from being freed,
>> -		 * otherwise we'll refresh it from
>> -		 * on-disk bitmap and lose not-yet-available
>> -		 * blocks */
>> -		page_cache_get(e4b->bd_buddy_page);
>> -		page_cache_get(e4b->bd_bitmap_page);
>> -	}
>>  	while (*n) {
>>  		parent = *n;
>>  		entry = rb_entry(parent, struct ext4_free_data, node);
>
>
> -aneesh
>
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