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

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Message-ID: <87aatxd4iq.fsf@linux.vnet.ibm.com>
Date:	Wed, 24 Mar 2010 22:46:13 +0530
From:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	jing zhang <zj.barak@...il.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Cc:	"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()

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.

> 
> 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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