On 18.10.21 г. 17:41, David Sterba wrote:

This is send protocol update to version 2 with example new commands.

We have many pending protocol update requests but still don't have the
basic protocol rev in place, the first thing that must happen is to do
the actual versioning support. In order to have something to test,
there's an extended and a new command, that should be otherwise harmless
and nobody should depend on it. This should be enough to validate the
non-protocol changes and backward compatibility before we do the big
protocol update.

The protocol version is u32 and is a new member in the send ioctl
struct. Validity of the version field is backed by a new flag bit. Old
kernels would fail when a higher version is requested. Version protocol
0 will pick the highest supported version, BTRFS_SEND_STREAM_VERSION,
that's also exported in sysfs.

W.r.t to the bits which add the infrastructure to do versioned support
you have an ACK from me. In the final submission I'd like to see those
bits separate from the rest of the code which implements particular
protocol changes, once this lands then Omar can also base his code on
the added infrastructure.