linux-ext4 - Re: [PATCH] ext4: memory leakage in ext4_mb

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Date:	Fri, 26 Mar 2010 22:40:30 +0800
From:	jing zhang <zj.barak@...il.com>
To:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	tytso@....edu, linux-ext4 <linux-ext4@...r.kernel.org>,
	Andreas Dilger <adilger@....com>,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
Subject: Re: [PATCH] ext4: memory leakage in ext4_mb_init()

2010/3/26, Aneesh Kumar K. V <aneesh.kumar@...ux.vnet.ibm.com>:
> On Tue, 23 Mar 2010 20:47:39 +0800, jing zhang <zj.barak@...il.com> wrote:
>> 2010/3/22, tytso@....edu <tytso@....edu>:
>> > On Sun, Mar 21, 2010 at 10:01:06PM +0800, jing zhang wrote:
>> >> From: Jing Zhang <zj.barak@...il.com>
>> >>
>> >> Date: Sun Mar 21 21:59:35     2010
>> >>
>> >> 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/mballoc3.c	2010-03-21 21:37:18.000000000 +0800
>> >> @@ -2360,6 +2360,24 @@ err_freesgi:
>> >>  	return -ENOMEM;
>> >>  }
>> >>
>> >> +static void ext4_mb_destroy_backend(struct super_block *sb)
>> >> +{
>> >> +	ext4_group_t ngroups = ext4_get_groups_count(sb);
>> >> +	ext4_group_t i;
>> >> +	struct ext4_sb_info *sbi = EXT4_SB(sb);
>> >> +	int j;
>> >> +	int num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) -1)
>> >> +					>> EXT4_DESC_PER_BLOCK_BITS(sb);
>> >> +	for (i = 0; i < ngroups; i++)
>> >> +		kfree(ext4_get_group_info(sb, i));
>> >> +
>> >> +	for (j = 0; j < num_meta_group_infos; j++)
>> >> +		kfree(sbi->s_group_info[j]);
>> >> +
>> >> +	kfree(sbi->s_group_info);
>> >> +	iput(sbi->s_buddy_cache);
>> >> +}
>> >> +
>> >
>> > It would be better if this could be done by making ext4_mb_release()
>> > more flexible, and then calling ext4_mb_release() if there is an error
>> > setting up the data structures in ext4_mb_init().
>> >
>> > 						- Ted
>> >
>>
>> Yeah, Ted, going through ext4_mb_release() is clearer.
>>
>> ---
>>
>> diff --git a/linux-2.6.32/fs/ext4/mballoc.c b/ext4_mm_leak/mballoc3.c
>> index bba1282..99ca2de 100644
>> --- a/linux-2.6.32/fs/ext4/mballoc.c
>> +++ b/ext4_mm_leak/mballoc3.c
>> @@ -2417,8 +2417,7 @@ int ext4_mb_init(struct super_block *sb, int
>> needs_recovery)
>>
>>  	sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);
>>  	if (sbi->s_locality_groups == NULL) {
>> -		kfree(sbi->s_mb_offsets);
>> -		kfree(sbi->s_mb_maxs);
>> +		ext4_mb_release(sb);
>
> We may want to make sure that we can safely call ext4_mb_release that
> early. what i would suggest is to move s_locality_group allocation
> before ext4_mb_init. that makes error handling easy
>

I will try what you suggest next week.

         - zj

>
>
>>  		return -ENOMEM;
>>  	}
>>  	for_each_possible_cpu(i) {
>> @@ -2511,7 +2510,8 @@ int ext4_mb_release(struct super_block *sb)
>>  				atomic_read(&sbi->s_mb_discarded));
>>  	}
>>
>> -	free_percpu(sbi->s_locality_groups);
>> +	if (sbi->s_locality_groups)
>> +		free_percpu(sbi->s_locality_groups);
>>  	if (sbi->s_proc)
>>  		remove_proc_entry("mb_groups", sbi->s_proc);
>> --
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>
> -aneesh
>
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