linux-ext4 - Re: hole punching in ext4

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Date:	Tue, 22 Jan 2013 17:03:12 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	"Bradley C. Kuszmaul" <kuszmaul@...il.com>
Cc:	Zheng Liu <gnehzuil.liu@...il.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: hole punching in ext4

On 2013-01-22, at 4:50 PM, Bradley C. Kuszmaul wrote:
> Thanks, this has been a very helpful thread.
> 
> How do I determine and control whether a file is extent-based?

You can use "lsattr" on the file, and look for the "e" attribute.

This should be standard for any ext4-formatted filesystem.  For
filesystems upgraded from ext3, you need to "tune2fs -O extents"
to enable this feature.

Cheers, Andreas

> On Tue, Jan 22, 2013 at 11:20 AM, Zheng Liu <gnehzuil.liu@...il.com> wrote:
>> Ext4 file system supports hole punching.  But until now only extent-based
>> file supports it.  As far as I know, redhat distributions don't support
>> hole punching.  You can find a sample program from e2fsprogs which is in
>> $e2fsprogs/conrib/fallocate.c.  The latest fallocate(1) in util-linux
>> also can be as a demo.
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