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

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Date:	Fri, 13 May 2011 17:55:36 +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

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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