linux-kernel - Re: [PATCH v6 4/7] fat: restructure export

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Date:	Mon, 18 Feb 2013 23:03:45 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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 v6 4/7] fat: restructure export_operations

2013/2/18 OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>:
> Namjae Jeon <linkinjeon@...il.com> writes:
>
>> +     if (MSDOS_SB(inode->i_sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
>> +             if (inode->i_ino == MSDOS_ROOT_INO)
>> +                     stat->ino = MSDOS_ROOT_INO;
>
> Can we simply set i_pos = MSDOS_ROOT_INO in fat_read_root()? If so, I
> think we can avoid this check.
Yes,  we can. I will change it.

>
>> +             else
>> +                     /* Use i_pos for ino. This is used as fileid of nfs. */
>> +                     stat->ino = fat_i_pos_read(MSDOS_SB(inode->i_sb),
>> +                                                inode);
>> +     }
>>       return 0;
>>  }
>>  EXPORT_SYMBOL_GPL(fat_getattr);
>
>
>> +struct fat_fid {
>> +     u32 i_gen;
>> +     u32 i_pos_low;
>> +     u16 i_pos_hi;
>> +     u16 parent_i_pos_hi;
>> +     u32 parent_i_pos_low;
>> +     u32 parent_i_gen;
>> +} __packed;
>
> Do we need to use __packed? Unnecessary __packed can generate slower
> code for alignment check on arch has unaligned fault.
Actually, I referenced other filesystem's exportfs code like btrfs and xfs.
they are packing their fids.
your opinion is reasonable, so I can fix it as your opinion.
>
>> +     if (parent && (len < FAT_FID_SIZE_WITH_PARENT)) {
>> +             *lenp = FAT_FID_SIZE_WITH_PARENT;
>> +             return 255;
>> +     } else if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
>> +             *lenp = FAT_FID_SIZE_WITHOUT_PARENT;
>> +             return 255;
>> +     }
>
> This check strange. "parent && len == FAT_FID_SIZE_WITHOUT_PARENT" will
> overwrite over limit of fh size?
I need to check more. because I followed the logic in
export_encode_fh() function.

Thanks for review!
> --
> OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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