In the new API is there a way to distinguish between the two copy offload behaviors: 1) FSCTL_DUPLICATE_EXTENTS (where the server file system increments a refcount on blocks in the range) and 2) FSCTL_COPYCHUNK (where the server does a server side copy of the requested range, but does not necessarily use reflink, although in the case of Samba on btrfs it implements it this way). In this case NTFS will usually make a copy of the range requested rather than linking the ranges. For the former cifs uses (used prior to this patc) the btrfs ioctl, for the latter it has a private ioctl (CIFS_IOC_COPYCHUNK_FILE). For the former the files have to be on the same share (export) for the latter it just requires that the files be on the same server, and in common cases (drag an drop in the file explorer on the desktop) the source and target files would be on different mounts to the same server. There is an unimplemented (in cifs.ko) whole file clone operation (copy-on-write file with a network API similar to the hardlink) but it looks like it is no longer supported by newer servers, perhaps because there is more interest in the ODX mechanism for duplicating files ala https://msdn.microsoft.com/en-us/library/windows/desktop/hh848056(v=vs.85).aspx across server farms for managing virtualization images. I need to add the ODX copy offload mechanism to cifs.ko but presumably it would behave more like FSCTL_COPYCHUNK (ie not do a reflink of the blocks) The performance improvements from server side copy offload is huge whether or not reflink is done - so allowing the cp command (or common user space commands ala robocopy which already does this in Windows) to do fast copy is particularly important for network file systems. On Thu, Nov 26, 2015 at 12:50 PM, Christoph Hellwig <hch@xxxxxx> wrote: > This patch set moves the existing btrfs clone ioctls that other file > system have started to implement to common code, and allows the NFS > server to export this functionality to remote systems. > > This work is based originally on my NFS CLONE prototype, which reused > code from Anna Schumaker's NFS COPY prototype, as well as various > updates from Peng Tao to this code. > > The patches are also available as a git branch and on gitweb: > > git://git.infradead.org/users/hch/pnfs.git clone-for-viro > http://git.infradead.org/users/hch/pnfs.git/shortlog/refs/heads/clone-for-viro > > -- > To unsubscribe from this list: send the line "unsubscribe linux-cifs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Thanks, Steve -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
