> -----Original Message----- > From: linux-cifs-owner@xxxxxxxxxxxxxxx <linux-cifs-owner@xxxxxxxxxxxxxxx> On > Behalf Of Aurélien Aptel > Sent: Friday, May 31, 2019 6:49 AM > To: Darrick J. Wong <darrick.wong@xxxxxxxxxx>; sfrench@xxxxxxxxx; > anna.schumaker@xxxxxxxxxx; trond.myklebust@xxxxxxxxxxxxxxx; > fengxiaoli0714@xxxxxxxxx > Cc: fstests@xxxxxxxxxxxxxxx; Murphy Zhou <xzhou@xxxxxxxxxx>; linux- > cifs@xxxxxxxxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx; linux-fsdevel <linux- > fsdevel@xxxxxxxxxxxxxxx> > Subject: Re: NFS & CIFS support dedupe now?? Was: Re: [PATCH] generic/517: > notrun on NFS due to unaligned dedupe in test > > "Darrick J. Wong" <darrick.wong@xxxxxxxxxx> writes: > > (Not sure about cifs, since I don't have a Windows Server handy) > > > > I'm not an expert in CIFS or NFS, so I'm asking: do either support > > dedupe or is this a kernel bug? > > AFAIK, the SMB protocol has 2 ioctl to do server side copies: > - FSCTL_SRV_COPYCHUNK [1] generic > - FSCTL_DUPLICATE_EXTENTS_TO_FILE [2], only supported on windows "new" > CoW > filesystem ReFS Windows also supports the T10 copy offload, when the backend storage (e.g. a SAN) supports it. There is no explicit support for dedup in SMB, that is considered a backend storage function and is not surfaced in the protocol. There are, however, some attributes relevant to dedup which are passed through. Tom.
