Linux-HyperV Archive on lore.kernel.org
 help / color / Atom feed
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
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

  reply index

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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=DM5PR21MB013798776480FFA5DCD22442D7960@DM5PR21MB0137.namprd21.prod.outlook.com \
    --to=mikelley@microsoft.com \
    --cc=davem@davemloft.net \
    --cc=decui@microsoft.com \
    --cc=haiyangz@microsoft.com \
    --cc=kys@microsoft.com \
    --cc=linux-hyperv@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=parri.andrea@gmail.com \
    --cc=sashal@kernel.org \
    --cc=sthemmin@microsoft.com \
    --cc=vkuznets@redhat.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-HyperV Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-hyperv/0 linux-hyperv/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-hyperv linux-hyperv/ https://lore.kernel.org/linux-hyperv \
		linux-hyperv@vger.kernel.org
	public-inbox-index linux-hyperv

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-hyperv


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git