Messages in this thread | | | Date | Thu, 21 Feb 2013 23:05:31 +0100 | From | Ric Wheeler <> | Subject | Re: New copyfile system call - discuss before LSF? |
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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
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