Date: Wed, 12 Dec 2007 09:15:55 +1100
From: David Chinner <dgc@sgi.com>
To: David Sparks <dave@ca.sophos.com>
Cc: xfs@oss.sgi.com
Subject: Re: mkfs.xfs ... lazy-count=1 ... not mountable by older kernels?
Message-ID: <20071211221554.GC4612@sgi.com>
References: <475EE83A.3060607@ca.sophos.com>
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On Tue, Dec 11, 2007 at 11:42:50AM -0800, David Sparks wrote:
> Hi all,
> 
> Is it expected that filesystems made with lazy-count=1 are not mountable by
> older kernels?

That is expected. lazy-count is a mkfs option because it changes the on-disk
format slightly, and older kernels do not understand that format. Hence
mkfs sets a superblock feature bit to prevent the filesystem from being
mounted on kernels that don't understand the slightly different disk format.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group