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Date:	Wed, 16 May 2012 23:10:16 +0800
From:	Tao Ma <tm@....ma>
To:	Andreas Dilger <adilger@...ger.ca>
CC:	linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH] ext4: Protect group inode free counting with group lock.

On 05/16/2012 10:58 PM, Andreas Dilger wrote:
> On 2012-05-16, at 2:49 AM, Tao Ma wrote:
>> From: Tao Ma <boyu.mt@...bao.com>
>>
>> Now when we set the group inode free count, we don't have a proper
>> group lock so that multiple threads may decrease the inode free
>> count at the same time. And e2fsck will complain something like:
>>
>> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
>> index 409c2ee..25595e2 100644
>> --- a/fs/ext4/ialloc.c
>> +++ b/fs/ext4/ialloc.c
>> @@ -772,7 +772,9 @@ got:
>> 			ext4_itable_unused_set(sb, gdp,
>> 					(EXT4_INODES_PER_GROUP(sb) - ino));
>> 		up_read(&grp->alloc_sem);
>> -	}
>> +	} else
>> +		ext4_lock_group(sb, group);
> 
> Minor coding style fix - when one half of if/else is using braces
> then the other half should also use braces, like:
> 
> 	if {
> 		:
> 	} else {
> 		:
> 	}
thank you Andreas, and I will change it in the next version.

Thanks
Tao
> 
>> +
>> 	ext4_free_inodes_set(sb, gdp, ext4_free_inodes_count(sb, gdp) - 1);
>> 	if (S_ISDIR(mode)) {
>> 		ext4_used_dirs_set(sb, gdp, ext4_used_dirs_count(sb, gdp) + 1);
>> @@ -782,10 +784,9 @@ got:
>> 			atomic_inc(&sbi->s_flex_groups[f].used_dirs);
>> 		}
>> 	}
>> -	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
>> +	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
>> 		gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
>> -		ext4_unlock_group(sb, group);
>> -	}
>> +	ext4_unlock_group(sb, group);
>>
>> 	BUFFER_TRACE(inode_bitmap_bh, "call ext4_handle_dirty_metadata");
>> 	err = ext4_handle_dirty_metadata(handle, NULL, inode_bitmap_bh);
>> -- 
>> 1.7.1
>>
>> --
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> 
> 
> Cheers, Andreas
> 
> 
> 
> 
> 
> --
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