Re: [PATCH 0/4] Fiemap, an extent mapping ioctl - round 2

[Dave Chinner <david@fromorbit.com>]

On Thu, Jun 26, 2008 at 09:03:49AM -0500, Eric Sandeen wrote:
> Mark Fasheh wrote:
> > Hello,
> > 
> > 	The following patches are the latest attempt at implementing a
> > fiemap ioctl, which can be used by userspace software to get extent
> > information for an inode in an efficient manner.
> > 
> > 	These patches are against 2.6.26-rc3, though they probably apply
> > fine against Linus' latest tree. The fs patches are much more complete this
> > time around, and the vfs patch has been trimmed down.
> > 
> > 	An updated version of my ioctl wrapper test program is available at:
> > 
> >    http://www.kernel.org/pub/linux/kernel/people/mfasheh/fiemap/tests/
> > 
> > 	A couple of notes regarding the VFS patch:
> > 
> > 	Firstly, most behavior-changing fm_flags have been removed. We're
> > left with SYNC and XATTR now. This is a very good thing because frankly, I
> > think fiemap should be targeted as a straight-forward and relatively
> > uncomplicated API for exposing extents as they appear on disk. Think "one
> > notch above extent-based FIBMAP replacement".
> 
> So Mark's gonna hate me for this 'cause I was acting all resigned last
> night, but I have to throw this out (sorry Mark!)
> 
> Right now the interface seems to be about returning details of the
> filesystem's accounting of the on-disk layout, as opposed to just a
> simple mapping.  As 2 examples:

IMO we shouldn't complicate the kernel implementation - if the user
wants to see merged extents, merge them in userspace. If the user
want's trimmed extents, do it in userspace. If the use wants
every raw extent, then nothing else needs to be done...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com