From: Michael Kelley <mikelley@microsoft.com>
To: Andrea Parri <parri.andrea@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Cc: KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Sasha Levin <sashal@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
vkuznets <vkuznets@redhat.com>, Dexuan Cui <decui@microsoft.com>
Subject: RE: [PATCH v2 1/3] Drivers: hv: vmbus: Introduce table of VMBus protocol versions
Date: Sat, 12 Oct 2019 13:47:45 +0000 [thread overview]
Message-ID: <DM5PR21MB013798776480FFA5DCD22442D7960@DM5PR21MB0137.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20191010154600.23875-2-parri.andrea@gmail.com>
From: Andrea Parri <parri.andrea@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 <mikelley@microsoft.com>
> Signed-off-by: Andrea Parri <parri.andrea@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
next prev parent reply other threads:[~2019-10-12 13:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 15:45 [PATCH v2 0/3] Drivers: hv: vmbus: Miscellaneous improvements Andrea Parri
2019-10-10 15:45 ` [PATCH v2 1/3] Drivers: hv: vmbus: Introduce table of VMBus protocol versions Andrea Parri
2019-10-12 13:47 ` Michael Kelley [this message]
2019-10-14 9:52 ` Andrea Parri
2019-10-10 15:45 ` [PATCH v2 2/3] Drivers: hv: vmbus: Enable VMBus protocol versions 4.1, 5.1 and 5.2 Andrea Parri
2019-10-12 13:34 ` Michael Kelley
2019-10-14 10:09 ` Andrea Parri
2019-10-10 15:46 ` [PATCH v2 3/3] Drivers: hv: vmbus: Add module parameter to cap the VMBus version Andrea Parri
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