Re: [PATCH v2 net-next 1/8] net: bridge: vlan: notify switchdev only when something changed

On 15/02/2022 12:30, Vladimir Oltean wrote:

quoted

On Tue, Feb 15, 2022 at 12:12:11PM +0200, Nikolay Aleksandrov wrote:

quoted

On 15/02/2022 11:54, Vladimir Oltean wrote:

quoted

On Tue, Feb 15, 2022 at 10:54:26AM +0200, Nikolay Aleksandrov wrote:

quoted

quoted

+/* return true if anything will change as a result of __vlan_add_flags,
+ * false otherwise
+ */
+static bool __vlan_flags_would_change(struct net_bridge_vlan *v, u16 flags)
+{
+	struct net_bridge_vlan_group *vg;
+	u16 old_flags = v->flags;
+	bool pvid_changed;
 
-	return ret || !!(old_flags ^ v->flags);
+	if (br_vlan_is_master(v))
+		vg = br_vlan_group(v->br);
+	else
+		vg = nbp_vlan_group(v->port);
+
+	if (flags & BRIDGE_VLAN_INFO_PVID)
+		pvid_changed = (vg->pvid == v->vid);
+	else
+		pvid_changed = (vg->pvid != v->vid);
+
+	return pvid_changed || !!(old_flags ^ v->flags);
 }

These two have to depend on each other, otherwise it's error-prone and
surely in the future someone will forget to update both.
How about add a "commit" argument to __vlan_add_flags and possibly rename
it to __vlan_update_flags, then add 2 small helpers like __vlan_update_flags_precommit
with commit == false and __vlan_update_flags_commit with commit == true.
Or some other naming, the point is to always use the same flow and checks
when updating the flags to make sure people don't forget.

You want to squash __vlan_flags_would_change() and __vlan_add_flags()
into a single function? But "would_change" returns bool, and "add"
returns void.

Hence the wrappers for commit == false and commit == true. You could name the precommit
one __vlan_flags_would_change or something more appropriate. The point is to make
sure we always update both when flags are changed.

I still have a little doubt that I understood you properly.
Do you mean like this?

By the way I just noticed that __vlan_flags_would_change has another bug, it's testing
vlan's flags against themselves without any change (old_flags == v->flags).

I meant something similar to this (quickly hacked, untested, add flags probably
could be renamed to something more appropriate):

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 1402d5ca242d..1de69090d3cb 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c

+}
+
+static bool __vlan_flags_would_change(struct net_bridge_vlan *v, u16 flags)
+{
+       return __vlan_add_flags(v, flags, false);
+}
+
+static bool __vlan_flags_commit(struct net_bridge_vlan *v, u16 flags)
+{

+       return __vlan_add_flags(v, flags, true);
 }
 
 static int __vlan_vid_add(struct net_device *dev, struct net_bridge *br,