[PATCH] smb2 FSCTL_SRV_COPYCHUNK support

[Volker Lendecke]

On Wed, Feb 15, 2012 at 02:00:51PM +0100, David Disseldorp wrote:
> On Wed, 15 Feb 2012 13:49:03 +0100
> Volker Lendecke <Volker.Lendecke at SerNet.DE> wrote:
> 
> > On a second thought: Why do we need copychunk in the VFS at
> > all? We have pread and pwrite in both sync and async
> > flavor. We could handle the copychunk stuff in the core smbd
> > building upon those. Or are there native file systems that
> > do copychunk?
> 
> Yes, btrfs via the BTRFS_IOC_CLONE_RANGE ioctl, and better yet it's
> only a metadata operation. This is plumed in as part of the patchset.
> Other COW based filesystems (ZFS etc.) may go down a similar path.

Ok, that might be fast enough to be done in a sync fashion.
The default implementation though would probably do it via
pread/pwrite which might be just slow enough to justify it
to be done asynchronously.

Volker

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