Re: New copyfile system call - discuss before LSF?

From: Jeremy Allison
Date: Thu Feb 21 2013 - 13:37:32 EST

On Thu, Feb 21, 2013 at 01:51:53PM +0000, Myklebust, Trond wrote:
> On Thu, 2013-02-21 at 12:37 +0100, Ric Wheeler wrote:
> > We have debated the need to have a system call to allow for offloading copy
> > operations, for example to an NFS server (part to the new NFS 4.2
> > specification), SCSI target device (two different SCSI commands do this), local
> > file systems (reflink, etc) and I suspect many other possible parts of the stack
> > could implement this.
> 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.

What would be really nice is if sendfile allowed zero-copy
from network socket to a file descriptor. That would help
a *lot* of my small system OEMs (and no splice() just doesn't
cut it :-).

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