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

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Date:	Thu, 6 Feb 2014 15:41:11 +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>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v3 1/6] fat: add i_disksize to represent uninitialized size

2014-02-04, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>:
> OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> writes:
>
>>>> 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?
>
> BTW, even if above was right, I'm not checking whether updating
> ->i_disksize after cont_write_begin() is right fix or not.
I understand your concern. these can be mismatched.
But, when checking your doubt, I can not find any side effect.
I think that there is no issue regardless of alignment of two value,
in the cont_write_begin.
Could you please share any point I am missing ?
If you suggest checking point or test method, I can check more and
share the result.

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