linux-ext4 - Re: [PATCH] Get rid of extents mount option

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Message-ID: <20061011171638.GP22010@schatzie.adilger.int>
Date:	Wed, 11 Oct 2006 11:16:38 -0600
From:	Andreas Dilger <adilger@...sterfs.com>
To:	Dave Kleikamp <shaggy@...tin.ibm.com>
Cc:	Theodore Tso <tytso@....edu>, Andrew Morton <akpm@...l.org>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Get rid of extents mount option - try 2

On Oct 06, 2006  16:21 -0500, Dave Kleikamp wrote:
> EXT4: Get rid of extents mount option
> 
> Enabling an ext4 file system to use extents should be done with
> 'tune2fs -O extents' or 'mke2fs -O extents', not with a mount option

I would agree that the presence of INCOMPAT_EXTENTS should imply the
EXTENTS mount option, but it is also desirable to be able to turn this
off for testing.  In our internal patches we also have a "noextents"
mount option to disable extents at runtime even if "extents" was given
as a default mount option.

So, I would leave most of the code as-is (with "test_opt(sb, EXTENTS)"),
and just have ext3_fill_super() enable EXT4_MOUNT_EXTENTS if
INCOMPAT_EXTENTS is set.  This is a tiny bit tricky since parse_options()
is called before the superblock is read, so I suspect we'll need a
separate EXT4_MOUNT_NOEXTENTS to distinguish between no mount "extents"
option given and "noextents" disabling this.

The Opt_noextents handling would clear EXT4_MOUNT_EXTENTS, and vice versa.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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