linux-kernel - Re: [PATCH v2] fat: eliminate iterations in fat_search_long and __fat

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Date:	Sat, 9 Feb 2013 11:15:43 +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>
Subject: Re: [PATCH v2] fat: eliminate iterations in fat_search_long and
 __fat_readdir in case of EOD

2013/2/8, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>:
> Namjae Jeon <linkinjeon@...il.com> writes:
>
>>> And did this work correctly about f_pos for readdir?
>> Yes, sure. f_pos is work correctly about each directory entry. because
>> after name[0] == 0x00, there are no allocated directory entires.
>>>
>>> I'm not thinking about f_pos deeply though, it may have something
>>> wrong. Because it stops at middle of cluster.
>> Plz See the below descirption about name[0] in FAT spec.
>> ---------------------------------------------------------------------------------------------------------------------
>> If DIR_Name[0] == 0x00, then the directory entry is free (same as for
>> 0xE5), and there are no allocated directory entries after this one
>> (all of the DIR_Name[0] bytes in all of the entries after this one are
>> also set to 0).
>> The special 0 value, rather than the 0xE5 value, indicates to FAT file
>> system driver code that the rest of the entries in this directory do
>> not need to be examined because they are all free.
>> -----------------------------------------------------------------------------------------------------------------------
>>
>> I think that lookuping entry till the end of cluster is not needed.
>> Let me know your opinion.
>
> I know it though. There is seek() and broken drivers adds entries after
> name[0] == 0. I think we don't need to care much about broken drivers
> though. Even if so, kernel should not be crash, and corrupts fs more.
Yes, Right. I understood. Plz ignore this patch.
>
>> And Would you tell me your opinion about fat exportfs ?
>
> Ah, I was thinking I did. But it seems I didn't actually. Can you post
> full of series? So, I can review and probably we can start to test it.
Okay, I will post full patch-set today.

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