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Date: Mon, 27 Apr 2015 08:25:58 +0800
From: Qu Wenruo <quwenruo@cn.fujitsu.com>
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To: <dsterba@suse.cz>, <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] btrfs: Fix superblock csum type check.
References: <1429837961-2255-1-git-send-email-quwenruo@cn.fujitsu.com> <20150424150507.GQ4996@twin.jikos.cz>
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-------- Original Message  --------
Subject: Re: [PATCH v2 1/2] btrfs: Fix superblock csum type check.
From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2015年04月24日 23:05

> On Fri, Apr 24, 2015 at 09:12:40AM +0800, Qu Wenruo wrote:
>> --- a/fs/btrfs/ctree.h
>> +++ b/fs/btrfs/ctree.h
>> @@ -173,6 +173,7 @@ struct btrfs_ordered_sum;
>>
>>   /* csum types */
>>   #define BTRFS_CSUM_TYPE_CRC32	0
>> +#define BTRFS_CSUM_LAST_TYPE	0
>>
>>   static int btrfs_csum_sizes[] = { 4, 0 };
>
> I'd prefer to fix it by removing the 0 from btrfs_csum_sizes instead of
> introducing a define.
>

Removing the zero seems not help for this case, as some one can still
craft a strange csum_type to access outside the array.

So I introduce the new macro and use the new macro to compare with 
csum_type without acess the array.

Thanks,
Qu