On Tue, May 08, 2018 at 09:16:46AM +1000, Dave Chinner wrote: > This sort of whacky undefined behaviour w.r.t. sparseness was the > reason we were given at LSFMM for cp and rsync not implementing > copy_file_range() - they could not control it according to the > user's direction. Hence my suggestion that we need flags to > specifically direct the behaviour of the syscall so that userspace > will actually use it.... They can just use SEEK_HOLE/DATA and just copy the chunk they care about. Especially as they already have the SEEK_HOLE/DATA logic for the plain old copy anyway - that is the only thing they have to create holes in the destination file to start with. Nevermind that a file system with inline dedup will happily create holes for them underneath.
