New ioctl - FSCTL_DUPLICATE_EXTENTS_TO_FILE
ddiss at suse.de
Wed Jan 28 11:22:03 MST 2015
On Tue, 27 Jan 2015 12:23:55 -0600, Steve French wrote:
> Has anyone tried the new ioctl (MS-FSCC) defined in the most recent
> update. See section 2.3.7
> Looks interesting for a new variant of copy offload
> "A new File System Control (FSCTL) has been added to support the new
> FSCTL_DUPLICATE_EXTENTS_TO_FILE operation in [MS-FSA]."
I haven't played with it yet, but from the [MS-FCC] 20150119 preview
doc it looks very similar to copy-chunk, with a few small differences:
- It's only supported on ReFS, which may indicate that it's implemented
using COW clones.
- It takes a regular file handle for the source, instead of requiring a
preliminary SRV_REQUEST_RESUME_KEY exchange.
- Only a single chunk can be duplicated per request, rather than
- Overlapping ranges are not supported.
- The length field is 64-bits wide, instead of 32.
- The response only carries the status code. This may imply there is no
server-advertised limit to the length of the request, further
indicating that it's COW based.
Time to start poking around with smbtorture :)
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