Re: [RFC] [patch 2/3] change attribute for ext4: ext4 specific code

[Cordenner jean noel <jean-noel.cordenner@bull.net>]

Theodore Tso a écrit :
> On Wed, Dec 13, 2006 at 06:31:50PM +0100, Cordenner jean noel wrote:
> 
> There was discussion on yesterday's call about whether or not 32-bit
> was enough for NFSv4, or whether it also requried 64-bits of change
> notification in the RFC's.  So one of the questions is whether this is
> something that would justify requiring 64-bits --- and if so, maybe we
> need to require that big inodes be used and store the entire 64-bit
> value beyond 128 bytes.  This would mean that NFSv4 cache management
> couldn't be fully implemented without big inodes, or we'd have to make
> do by using the inode ctime as a partial substitute.
> 
> What do you think?
> 
> 						- Ted
> 

Well it seems that NFSv4 RFC requires a 64-bits notification.
The interest of the change attribute is that it has a simple 
implementation and doesn't seem to penalize the performance.
Using a 32bits counter and the ctime can give a resolution less than ns.

But it seems to me that finner timestamp could be usefull in the future. 
As the ns patch also use a counter, I don't know if a common 
implementation would avoid using big inode.

I agree with Andreas saying that the "change_attribute" can be stored in 
the i_version field.

Jean noel