linux-ext4 - Re: [PATCH] Add flag to files with blocks intentionally past EOF

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Date:	Wed, 20 Jan 2010 16:37:03 +0800
From:	Andreas Dilger <adilger@....com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Mingming <cmm@...ibm.com>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Add flag to files with blocks intentionally past EOF

On 2010-01-20, at 11:58, Eric Sandeen wrote:
> Mingming wrote:
>>
>> I am a little lost why doing vmtruncate here...
>
> Hm first off I assume vmtruncate will clear blocks past that size,
> but tonight I'm not seeing how it gets there.
>
> Anyway, it looks like any setting of the size, truncate up or down
> (or to current size) will clear any blocks past EOF.


Why not just call ext4_truncate(inode)?  Since these blocks are only  
fallocated, and pages couldn't (shouldn't?) be instantiated beyond  
i_size, we don't need to do anything at the mapping level, only at the  
inode level.

> Well here we are clearing the EOFBLOCKS flag so we'd want to clear any
> blocks past EOF.... but now, does vmtruncate do that?
>
> Ok, count me as confused too, but mostly jsut so far as how does
> vmtruncate clear the blocks beyond eof.  I guess I glossed over this  
> when reading it.


Has the new truncate API patchset gone into the kernel?  I recall  
there was some work to restructure the API and maybe you are a victim  
of understanding the old API?

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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