linux-ext4 - Re: [Ext4 punch hole 1/5] Ext4 Punch Hole Support: Convert Blocks to Uninit Exts

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Message-Id: <4CB90DB0-DA5C-4A64-9DC0-53F46BE40915@dilger.ca>
Date:	Wed, 2 Mar 2011 17:56:52 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	Dave Chinner <david@...morbit.com>
Cc:	Allison Henderson <achender@...ux.vnet.ibm.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [Ext4 punch hole 1/5] Ext4 Punch Hole Support: Convert Blocks to Uninit Exts

On 2011-03-02, at 13:23, Dave Chinner <david@...morbit.com> wrote:
> On Mon, Feb 28, 2011 at 11:42:48PM -0700, Andreas Dilger wrote:
>> On 2011-02-28, at 8:08 PM, Allison Henderson wrote:
>>> This first patch adds a function to convert a range of blocks
>>> to an uninitialized extent.  This function will
>>> be used to first convert the blocks to extents before
>>> punching them out.
>> 
>> This was proposed as a separate function for FALLOCATE by Dave
>> Chinner (based on XFS_IOC_ZERO_RANGE), so this is useful as a
>> standalone function.
> 
> XFS_IOC_ZERO_RANGE converts a range to unwritten extents, not
> uninitialised extents. An uninitialised extent is one that is
> allocated but had not data written to it (i.e. contains stale data),
> while an unwritten/preallocated extent is guaranteed to contain
> zeros.

For ext4 at least there is no distinction at least. Still, it is good to use the right terms so that we are all on the same page. 

>  This may be just a terminology issue, but we should try to
> use the same jargon across all filesystems...

Cheers, Andreas--
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