linux-ext4 - Re: [PATCH] ext4: invalidate gap cache when writing extents last block

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Message-ID: <4DDB6D66.3010703@sx.jp.nec.com>
Date:	Tue, 24 May 2011 17:33:42 +0900
From:	Kazuya Mio <k-mio@...jp.nec.com>
To:	Lukas Czerner <lczerner@...hat.com>
CC:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH] ext4: invalidate gap cache when writing extents last
 block

Hi Lukas,
How do you think about my comment?

Regards,
Kazuya Mio

2011/05/13 17:55, Kazuya Mio wrote:
> 2011/05/13 15:36, Lukas Czerner wrote:
>> That is because due to defensive programming we planted a lot of
>> BUG_ON's to prevent the length of the gap cache to be zero, but in this
>> case it actually will be zero, because there will be no gap at the end
>> of the file.
> 
> Um, I think there is a block (blocksize -1 byte) in gap.
> And this gap should be used for the next block searching.
> According to ext4_ext_in_cache(), len=0 means the special case
> which we have no cache extent, so len=0 should be disallowed.
> 
> Moreover, if we create the file which has 2^32-1 offset,
> we can't get extent which starts from this offset with FIEMAP ioctl.
> That's why I think the maximum file size should be 2^32-1 * blocksize.
> 
> Regards,
> Kazuya Mio
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