Re: New copyfile system call - discuss before LSF?

[Ric Wheeler]

On 02/21/2013 09:00 PM, Paolo Bonzini wrote:
> Il 21/02/2013 15:57, Ric Wheeler ha scritto:
> > > sendfile64() pretty much already has the right arguments for a
> > > "copyfile", however it would be nice to add a 'flags' parameter: the
> > > NFSv4.2 version would use that to specify whether or not to copy file
> > > metadata.
> > That would seem to be enough to me and has the advantage that it is an
> > relatively obvious extension to something that is at least not totally
> > unknown to developers.
> >
> > Do we need more than that for non-NFS paths I wonder? What does reflink
> > need or the SCSI mechanism?
> For virt we would like to be able to specify arbitrary block ranges.
> Copying an entire file helps some copy operations like storage
> migration.  However, it is not enough to convert the guest's offloaded
> copies to host-side offloaded copies.
>
> Paolo

I don't think that the NFS protocol allows arbitrary ranges, but the SCSI 
commands are ranged based.

If I remember what the windows people said at a SNIA event a few years back, 
they have a requirement that the target file be pre-allocated (at least for the 
SCSI based copy). Not clear to me where they iterate over that target file to do 
the block range copies, but I suspect it is in their kernel.

Ric

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/