linux-ext4 - Re: [PATCH] ext4: memory leakage in ext4_mb_free

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Date:	Thu, 25 Mar 2010 22:09:38 +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: memory leakage in ext4_mb_free_blocks()

2010/3/25, Aneesh Kumar K. V <aneesh.kumar@...ux.vnet.ibm.com>:
> On Wed, 24 Mar 2010 21:55:55 +0800, jing zhang <zj.barak@...il.com> wrote:
>> From: Jing Zhang <zj.barak@...il.com>
>>
>> Date: Wed Mar 24 21:54:22     2010
>>
>> There is memory leakage in ext4_mb_free_blocks(), if error, double
>> free of blocks, occurs in ext4_mb_free_metadata().
>>
>> 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/mballoc8.c	2010-03-24 21:46:50.000000000 +0800
>> @@ -4419,7 +4419,8 @@ ext4_mb_free_metadata(handle_t *handle,
>>  	spin_lock(&sbi->s_md_lock);
>>  	list_add(&new_entry->list, &handle->h_transaction->t_private_list);
>>  	spin_unlock(&sbi->s_md_lock);
>> -	return 0;
>> +	/* info the caller new_entry is used */
>> +	return 1;
>>  }
>>
>
> return 0 on success and -1 on failure

Agree

>
>
>>  /*
>> @@ -4547,7 +4548,8 @@ do_more:
>>
>>  		ext4_lock_group(sb, block_group);
>>  		mb_clear_bits(bitmap_bh->b_data, bit, count);
>> -		ext4_mb_free_metadata(handle, &e4b, new_entry);
>> +		if (0 == ext4_mb_free_metadata(handle, &e4b, new_entry))
>> +			kmem_cache_free(ext4_free_ext_cachep,
>>  		new_entry);
>
> I guess  it would be better to be
>
> if (ext4_mb_free_metadat() == -1)
>    kmem_cache_free(..)

Fine
      - zj

>
>
>
>>  	} else {
>>  		/* need to update group_info->bb_free and bitmap
>>  		 * with group lock held. generate_buddy look at
>
>
> -aneesh
>
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