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

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Message-ID: <874nhn46qm.fsf@devron.myhome.or.jp>
Date:	Fri, 08 Feb 2013 16:14:41 +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>
Subject: Re: [PATCH v2] fat: eliminate iterations in fat_search_long and __fat_readdir in case of EOD

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.

> 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.

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