User Copy Mode and COMMIT_AND_FETCH interaction

[sargun]

Just so I understand, you still need to do the COMMIT_AND_FETCH command after the user copy, right?

So, the interaction flow goes something like this:

server->driver: FETCH_REQ
driver->server: descriptor for read
server->driver: pwritev($SPECIAL_OFFSET, buf)
server->driver: COMMIT_AND_FETCH(descriptor)

[ming1]

Yes.

Exactly, for READ, you need to call pwritev() to write data into the IO buffer.
for WRITE, you need to call preadv() to read data from the IO buffer.

USER_COPY just means the ublk_drv(kernel side) doesn't handle the IO
data copy.

thanks,