linux-ext4 - Re: [PATCH] ext4: memory leakage in ext4_discard

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Date:	Fri, 26 Mar 2010 14:07:31 +0530
From:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	jing zhang <zj.barak@...il.com>, Andreas Dilger <adilger@....com>
Cc:	tytso@....edu, linux-ext4 <linux-ext4@...r.kernel.org>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: Re: [PATCH] ext4: memory leakage in ext4_discard_preallocations

On Sat, 20 Mar 2010 22:05:13 +0800, jing zhang <zj.barak@...il.com> wrote:
> 
> Evening,
> 
> Thanks Andreas and Ted for your good explanations to deal error in
> gentle way, and I got it that the chance may exist since the pa is not
> deleted from its group_list yet.
> 
> And it also seems that there is work deserved.
>        - zj
> 
> ---
> 
> --- linux-2.6.32/fs/ext4/mballoc.c	2009-12-03 11:51:22.000000000 +0800
> +++ fs/mballoc.c	2010-03-20 21:40:04.000000000 +0800
> @@ -3788,14 +3788,14 @@ repeat:
>  		err = ext4_mb_load_buddy(sb, group, &e4b);
>  		if (err) {
>  			ext4_error(sb, __func__, "Error in loading buddy "
> -					"information for %u", group);
> +			"information for group %u inode %lu", group, inode->i_ino);
>  			continue;
>  		}
> 
>  		bitmap_bh = ext4_read_block_bitmap(sb, group);
>  		if (bitmap_bh == NULL) {
>  			ext4_error(sb, __func__, "Error in reading block "
> -					"bitmap for %u", group);
> +			"bitmap for group %u inode %lu", group, inode->i_ino);
>  			ext4_mb_release_desc(&e4b);
>  			continue;
>  		}
> @@ -3811,6 +3811,14 @@ repeat:
>  		list_del(&pa->u.pa_tmp_list);
>  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
>  	}
> +	if (! list_empty(&list)) {
> +		/*
> +		 * we have to do something for the check in
> +		 * the function, ext4_mb_discard_group_preallocations()
> +		 */
> +		list_for_each_entry(pa, &list, u.pa_tmp_list)
> +			pa->pa_deleted = 0;
> +	}
>  	if (ac)
>  		kmem_cache_free(ext4_ac_cachep, ac);
>  }

Can you add a comment saying if we fail to load buddy or read block
bitmap we skip freeing the prealloc space. So mark it undeleted. The
prealloc space is still removed from the inode but it is linked to the
group prealloc list via (pa_group_list)


-aneesh
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