Hi! This series is my initial attempt at getting a copy_file_range syscall implementation in the kernel cephfs client using the 'copy-from' RADOS operation. The idea of getting this implemented was from Greg -- or, at least, he created a feature in the tracker [1]. I just decided to give it a try as the feature wasn't assigned to anyone ;-) I have this patchset sitting on my laptop for a while already, waiting for me to revisit it, review some of its TODOs... but I finally decided to send it out as-is instead, to get some early feedback. The first patch implements the copy-from operation in the libceph module. Unfortunately, the documentation for this operation is nonexistent and I had to do a lot of digging to figure out the details (and I probably I missed something!). For example, initially I was hoping that this operation could be used to copy more than one object at the time. Doing an OSD request per object copy is not ideal, but unfortunately it seems to be the only way. Anyway, my expectations are that this new operation will be useful for other features in the future. The 2nd patch is where the copy_file_range is implemented and could probably be optimised, but I didn't bother with that for now. The important bit is that we still may need to do some manual copies if the offsets aren't object aligned or if the length is smaller than the object size. I'm using do_splice_direct() for the manual copies as it was the easiest way to get a PoC running, but maybe there are better ways. I've done some functional testing on this PoC. And it also passes the generic xfstest suite, in particular the copy_file_range specific tests (430-434). But I haven't done any benchmarks to measure any performance changes in using this syscall. Any feedback is welcome, specially regarding the TODOs on the code. [1] https://tracker.ceph.com/issues/21944 Luis Henriques (2): ceph: support the RADOS copy-from operation ceph: support copy_file_range file operation fs/ceph/file.c | 182 ++++++++++++++++++++++++++++++++ include/linux/ceph/osd_client.h | 18 ++++ include/linux/ceph/rados.h | 19 ++++ net/ceph/osd_client.c | 73 +++++++++++++ 4 files changed, 291 insertions(+)
