From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Disseldorp Subject: Re: New ioctl - FSCTL_DUPLICATE_EXTENTS_TO_FILE Date: Wed, 28 Jan 2015 19:22:03 +0100 Message-ID: <20150128192203.5dbb06ea@g21.suse.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "linux-cifs@vger.kernel.org" , samba-technical , David Disseldorp To: Steve French Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: samba-technical-bounces@lists.samba.org Errors-To: samba-technical-bounces@lists.samba.org List-Id: linux-cifs.vger.kernel.org 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 multiple. - 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 :) Cheers, David