linux-kernel - Re: [PATCH v3 1/6] fat: add i_disksize to represent uninitialized size

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Message-ID: <87y51rue2a.fsf@devron.myhome.or.jp>
Date:	Tue, 04 Feb 2014 23:50:53 +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>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v3 1/6] fat: add i_disksize to represent uninitialized size

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

> 2014-02-03, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>:
>> Namjae Jeon <linkinjeon@...il.com> writes:
>>
>>> From: Namjae Jeon <namjae.jeon@...sung.com>
>>>
>>> Add i_disksize to represent uninitialized allocated size.
>>> And mmu_private represent initialized allocated size.
>>
>> Don't we need to update ->i_disksize after cont_write_begin()?
> We don't need to update i_disksize after cont_write_begin.
> It is taken care by the fat_get_block after the allocation.
> For all write paths we align the mmu_private and i_disksize from
> fat_fill_inode and fat_get_block.

fat_fill_inode() just set i_disksize to i_size. So, it is not aligned by
cluster size or block size.

E.g. ->mmu_private = 500. Then, cont_write_begin() can set ->mmu_private
to 512 on some case. In this case, fat_get_block() will not be called,
because no new allocation.

If this is true, it would be possible to have ->mmu_private == 512 and
->i_disksize == 500. 

I'm missing something?

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