search for: nbd_flag_zero_is_fast

...s without issues). > > I understand that fail-on-first ENOTSUP is OK for raw-without-fallocte vs qcow2, > as first will always return ENOTSUP and second will never fail.. But in such way > we'll OK with simpler extension, which only have one server-advirtised negotiation > flag NBD_FLAG_ZERO_IS_FAST. Advertising that a server's zero behavior is always going to be successfully fast is a much harder flag to implement. The justification for the semantics I chose (advertising that the server can quickly report failure if success is not fast, but not requiring fast zero) covers the case when...

This is a cover letter to a series of patches being proposed in tandem to four different projects: - nbd: Document a new NBD_CMD_FLAG_FAST_ZERO command flag - qemu: Implement the flag for both clients and server - libnbd: Implement the flag for clients - nbdkit: Implement the flag for servers, including the nbd passthrough client If you want to test the patches together, I've pushed a