From: Andrea Parri <parri.and...@gmail.com> Sent: Thursday, October 10, 2019
8:46 AM
>
> The technique used to get the next VMBus version seems increasisly
> clumsy as the number of VMBus versions increases. Performance is
> not a concern since this is only done once during system boot; it's
> just that we'll end up with more lines of code than is really needed.
>
> As an alternative, introduce a table with the version numbers listed
> in order (from the most recent to the oldest). vmbus_connect() loops
> through the versions listed in the table until it gets an accepted
> connection or gets to the end of the table (invalid version).
>
> Suggested-by: Michael Kelley <mikel...@microsoft.com>
> Signed-off-by: Andrea Parri <parri.and...@gmail.com>
> ---
> drivers/hv/connection.c | 46 ++++++++++++++---------------------------
> drivers/hv/vmbus_drv.c | 3 +--
> include/linux/hyperv.h | 4 ----
> 3 files changed, 17 insertions(+), 36 deletions(-)
>
> @@ -244,20 +232,18 @@ int vmbus_connect(void)
> * version.
> */
>
> - version = VERSION_CURRENT;
> + for (i = 0; i < ARRAY_SIZE(vmbus_versions); i++) {
> + version = vmbus_versions[i];
>
> - do {
> ret = vmbus_negotiate_version(msginfo, version);
> if (ret == -ETIMEDOUT)
> goto cleanup;
>
> if (vmbus_connection.conn_state == CONNECTED)
> break;
> + }
>
> - version = vmbus_get_next_version(version);
> - } while (version != VERSION_INVAL);
> -
> - if (version == VERSION_INVAL)
> + if (vmbus_connection.conn_state != CONNECTED)
> goto cleanup;
>
This is a nit, but the loop exit path bugs me. When a connection
is established, the loop is exited by the "break", and then
conn_state has to be tested again to decide whether the loop
exited due to getting a connection vs. hitting the end of the list.
Slightly cleaner in my mind would be:
for (i=0; ; i++) {
if (i == ARRAY_SIZE(vmbus_versions))
goto cleanup;
version = vmbus_versions[i];
ret = vmbus_negotiate_version(msginfo, version);
if (ret == -ETIMEDOUT)
goto cleanup;
if (vmbus_connection.conn_state == CONNECTED)
break;
}
Michael
