On 12/14/2011 02:27 PM, Al Viro wrote:
On Wed, Dec 14, 2011 at 02:22:07PM -0500, Ric Wheeler wrote:
We had an active thread a couple of years back that came out of the
reflink work and, at the time, there seemed to be moderately
positive support for adding a new system call that would fit this
use case (Joel Becker's copyfile()).
Can we resurrect this effort? Is copyfile() still a good way to go,
or should we look at other hooks?
copyfile(2) is probably a good way to go, provided that we do _not_
go baroque as it had happened the last time syscall had been discussed.
IOW, to hell with progress reports, etc. - just a fastpath kind of
thing, in the same kind of relationship to cp(1) as rename(2) is to mv(1).
If it works - fine, if not - caller has to be ready to deal with handling
cross-device case anyway.
I think that this approach makes a lot of sense. Most of the devices/targets
that support the copy offload, will do it in very reasonable amounts of time.
Let me see if I can dig up some of the presentations from the NetApp guys who
presented overviews or the specifications from the IETF and T10....
Ric
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