[PATCH 2/2] xfs: Introduce XFS_IOC_ZERO_RANGE

[Christoph Hellwig]

On Tue, Jul 27, 2010 at 03:55:29PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> XFS_IOC_ZERO_RANGE is the equivalent of an atomic XFS_IOC_UNRESVSP/
> XFS_IOC_RESVSP call pair. It enabled ranges of written data to be
> turned into zeroes without requiring IO or having to free and
> reallocate the extents in the range given as would occur if we had
> to punch and then preallocate them separately.  This enables
> applications to zero parts of files very quickly without changing
> the layout of the files in any way.

This looks good minus the left over printks.  It'll also needs xfstests
coverage and a description in the xfsctl manpage.