linux-ext4 - Re: [PATCH] ext4: fix online resize group descriptors corruption

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Date:	Thu, 12 Jun 2008 16:56:55 +0200
From:	Jean-Pierre Dion <jean-pierre.dion@...l.net>
To:	Andreas Dilger <adilger@....com>
Cc:	frederic.bohe@....bull.net, tytso@....edu,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: fix online resize group descriptors corruption

Hi Andreas,

thank you for this review of Frédéric's patch
and your comments that help.

Frédéric just joined our team a few days ago and
this kind of help is very usefull.

Frédéric has not a great experience in Linux
but he has a strong one in embedded systems
and telecoms. Correct me where I am wrong Frédéric. ;-)


jean-pierre


Andreas Dilger a écrit :
> On Jun 12, 2008  11:42 +0200, Fr�d�ric Boh� wrote:
>   
>> From: Frederic Bohe <frederic.bohe@...l.net>
>>
>> This is the patch for the group descriptor table corruption during
>> online resize pointed out by Theodore Tso.
>> The issue was due to the ext4 group descriptor which can be either
>> 32 or 64 bytes long.
>> Only the 64 bytes structure was taken into account.
>>
>> diff -rup a/fs/ext4/resize.c b/fs/ext4/resize.c
>> --- a/fs/ext4/resize.c
>> +++ b/fs/ext4/resize.c
>> @@ -855,7 +855,8 @@ int ext4_group_add(struct super_block *s
>>  	 */
>>  
>>  	/* Update group descriptor block for new group */
>> -	gdp = (struct ext4_group_desc *)primary->b_data + gdb_off;
>> +	gdp = (struct ext4_group_desc *)(
>> +	       (__u8 *)primary->b_data + gdb_off * EXT4_DESC_SIZE(sb));
>>     
>
> Normally pointer arithmetic is done by casting to (char *)...
> Otherwise, patch looks sensible, though it could be reformatted to 
> match the normal coding style a bit better:
>
> 	gdp = (struct ext4_group_desc *)((char *)primary->b_data +
> 					 gdb_off * EXT4_DESC_SIZE(sb));
>
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
>
> --
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>
>   

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