On Mon, Oct 01, 2018 at 01:51:09PM -0600, Andreas Dilger wrote: > On Oct 1, 2018, at 9:49 AM, Eric Sandeen <sandeen@xxxxxxxxxxx> wrote: > > Yes, I would expect there to be problems with his modified kernel > > for a filesystem that supports clone_file_range, because > > vfs_copy_file_range() will clone if possible, and this should fail across > > filesystems. > > > > In general, though, I don't know for sure why we don't fall back to > > do_splice_direct() across filesystems, although the filesystems that > > implement their own ->copy_file_range ops may have their own, > > further restrictions within their implementations. > > > > This call /is/ documented in the manpage as only being valid for > > files on the same filesystem, though: > > http://man7.org/linux/man-pages/man2/copy_file_range.2.html > > There was a patch to allow cross-mount copy for NFS, but it hasn't landed > yet. I thought Christoph Hellwig vetoed it partly because he thought NFS server-to-server copy is too complicated. Which perhaps it is, but I suspect we'll do it anyway because the benefit seems obvious. --b.
