linux-kernel - Re: [PATCH v5 5/8] fat: restructure export

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Date:	Wed, 05 Dec 2012 17:56:55 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Ravishankar N <ravi.n1@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v5 5/8] fat: restructure export_operations

Namjae Jeon <linkinjeon@...il.com> writes:

>>> Let me think, if ‘subtree’ checking is enabled then we should check
>>> the length condition over here also? Please share if there are any
>>> other comments also.
>>
>> I'm not sure what did you mean. Where is "subtree" check you are
>> talking? This is fh_to_dentry(), so we don't use parent at all, so
>> length == 3 is enough?
> With fileID type="FILEID_FAT_WITHOUT_PARENT", fhlen  should be '3'
> With fileId type="FILEID_FAT_WITH_PARENT", fhlen should be '5'
>
> While encoding, WITH_PARENT is selected when subtree check is enabled
> on the NFS Server.
>
> So, when decoding request is arrived-  fileid type will be among the '2' cases:
> Now, in case of fh_to_dentry() - when we consider, that the reqquest
> for fileid type WITH_PARENT
> then i think the conditions in fh_to_dentry should be:
>
> if((fh_type == FILEID_FAT_WITH_PARENT) && fh_len != 5)
> 	return NULL;
> else if (fh_len != 3)
> 	return NULL;
>
> So, we took care of these '2' conditions within the switch statement
> based on the 'fh_type'. We can just change the comparision condition
> from '<' to '!=':
> switch (fh_type) {
> +	case FILEID_FAT_WITHOUT_PARENT:
> +		if (fh_len != FAT_FID_SIZE_WITHOUT_PARENT)
> +			return NULL;
> +	case FILEID_FAT_WITH_PARENT:
> +		if ((fh_len != FAT_FID_SIZE_WITH_PARENT) &&
> +			(fh_type == FILEID_FAT_WITH_PARENT))
> +			return NULL;
> +		i_pos = fid->i_pos_hi;
> +		i_pos = (i_pos << 32) | (fid->i_pos_low);
> +		inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);
> +		break;
> +	}
>
> I think there is no need to push the comparision statements in the
> begining similar to generic_fh_to_dentry.

I can understand what is doing. I'm asking why there is difference.

1) generic_fh_to_dentry() allows (*_PARENT && fh_len == 2).
2) fat_fh_to_dentry_nostale() doesn't allows (*_PARENT && fh_len == 3).

Why does logic has difference?
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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