Re: [RFC][PATCH 0/5] Fiemap, an extent mapping ioctl

[Mark Fasheh <mfasheh@suse.com>]

On Tue, May 27, 2008 at 12:45:46PM -0400, Christoph Hellwig wrote:
> > I don't see why we need a different ioctl for mapping extents on a
> > filesystem that support direct access to multiple disks.  Having one
> > mechanism that returns the file mapping is much more simple for user
> > space applications (filefrag, cp, tar, gzip, etc) than having to use
> > different ioctls for different backing filesystems.
> 
> Well, we could add a dev field that contains the dev_t for the
> underlying block device.  That would work for the current XFS realtime
> device aswell as for my work to map different XFS AGs to different
> devices.  It wouldn't work for btrfs with integrated raid code where
> a single extent can span multiple underlying devices, the same probably
> applies to pnfs.

Dev_t seems reasonable to me.

Anything any more complicated than just wanting a simple device identifier
needs a more dedicated API.
	--Mark

--
Mark Fasheh