linux-ext4 - Re: e4defrag and immutable files

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Date:	Tue, 01 Jun 2010 15:51:29 -0700
From:	Sunil Mushran <sunil.mushran@...cle.com>
To:	tytso@....edu
CC:	Eric Sandeen <sandeen@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-ext4@...r.kernel.org,
	Joel Becker <Joel.Becker@...cle.com>,
	Mark Fasheh <mfasheh@...e.com>
Subject: Re: e4defrag and immutable files

On 06/01/2010 03:26 PM, tytso@....edu wrote:
> On Tue, Jun 01, 2010 at 02:28:08PM -0700, Sunil Mushran wrote:
>    
>> We had thought of the term static because we wanted the inode to
>> be frozen. Entire metadata including the mapping. Our aim is to
>> do away with cluster locks for such inodes. For ios, we were planning
>> to limit it to only odirect and not change the mtime. That also means
>> no links, touch. Yes, "static" does not fit it like a glove but that's the
>> best we could come up with.
>>      
> Hmm, maybe "fixed_metadata"?  The one thing that worries a bit is not
> touching mtime is definitely icky.  I suppose it would improve
> performance even on local-disk file systems if we don't update mtime,
> ctime, or atime.  So maybe that would be useful for folks who are
> trying to extract the last bit of performance out of their enterprise
> database.
>
> One thing I do like about fixed_metadata is that as far as chattr and
> lsattr is concerned 's' and 'S' are already taken.  But 'f' and 'F'
> aren't allocated yet.  :-)
>
>    

Fixed Metadata sounds good to me.

The mtime restriction is icky. But for us it is a requirement
considering we cannot safely update it without cluster locks.
I am ok if we can make that file system specific.
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