net: switchdev: remove the transaction structure from port object notifiers

Since the introduction of the switchdev API, port objects were
transmitted to drivers for offloading using a two-step transactional
model, with a prepare phase that was supposed to catch all errors, and a
commit phase that was supposed to never fail.

Some classes of failures can never be avoided, like hardware access, or
memory allocation. In the latter case, merely attempting to move the
memory allocation to the preparation phase makes it impossible to avoid
memory leaks, since commit 91cf8eceffc1 ("switchdev: Remove unused
transaction item queue") which has removed the unused mechanism of
passing on the allocated memory between one phase and another.

It is time we admit that separating the preparation from the commit
phase is something that is best left for the driver to decide, and not
something that should be baked into the API, especially since there are
no switchdev callers that depend on this.

This patch removes the struct switchdev_trans member from switchdev port
object notifier structures, and converts drivers to not look at this
member.

Where driver conversion is trivial (like in the case of the Marvell
Prestera driver, NXP DPAA2 switch, TI CPSW, and Rocker drivers), it is
done in this patch.

Where driver conversion needs more attention (DSA, Mellanox Spectrum),
the conversion is left for subsequent patches and here we only fake the
prepare/commit phases at a lower level, just not in the switchdev
notifier itself.

Where the code has a natural structure that is best left alone as a
preparation and a commit phase (as in the case of the Ocelot switch),
that structure is left in place, just made to not depend upon the
switchdev transactional model.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 4 insertions, 38 deletions

diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index 23d868545362..a575bb33ee6c 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -221,7 +221,6 @@ static size_t switchdev_obj_size(const struct switchdev_obj *obj)
 static int switchdev_port_obj_notify(enum switchdev_notifier_type nt,
 				     struct net_device *dev,
 				     const struct switchdev_obj *obj,
-				     struct switchdev_trans *trans,
 				     struct netlink_ext_ack *extack)
 {
 	int rc;
@@ -229,7 +228,6 @@ static int switchdev_port_obj_notify(enum switchdev_notifier_type nt,
 
 	struct switchdev_notifier_port_obj_info obj_info = {
 		.obj = obj,
-		.trans = trans,
 		.handled = false,
 	};
 
@@ -248,35 +246,10 @@ static int switchdev_port_obj_add_now(struct net_device *dev,
 				      const struct switchdev_obj *obj,
 				      struct netlink_ext_ack *extack)
 {
-	struct switchdev_trans trans;
-	int err;
-
 	ASSERT_RTNL();
 
-	/* Phase I: prepare for obj add. Driver/device should fail
-	 * here if there are going to be issues in the commit phase,
-	 * such as lack of resources or support.  The driver/device
-	 * should reserve resources needed for the commit phase here,
-	 * but should not commit the obj.
-	 */
-
-	trans.ph_prepare = true;
-	err = switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_ADD,
-					dev, obj, &trans, extack);
-	if (err)
-		return err;
-
-	/* Phase II: commit obj add.  This cannot fail as a fault
-	 * of driver/device.  If it does, it's a bug in the driver/device
-	 * because the driver said everythings was OK in phase I.
-	 */
-
-	trans.ph_prepare = false;
-	err = switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_ADD,
-					dev, obj, &trans, extack);
-	WARN(err, "%s: Commit of object (id=%d) failed.\n", dev->name, obj->id);
-
-	return err;
+	return switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_ADD,
+					 dev, obj, extack);
 }
 
 static void switchdev_port_obj_add_deferred(struct net_device *dev,
@@ -307,10 +280,6 @@ static int switchdev_port_obj_add_defer(struct net_device *dev,
  *	@obj: object to add
  *	@extack: netlink extended ack
  *
- *	Use a 2-phase prepare-commit transaction model to ensure
- *	system is not left in a partially updated state due to
- *	failure from driver/device.
- *
  *	rtnl_lock must be held and must not be in atomic section,
  *	in case SWITCHDEV_F_DEFER flag is not set.
  */
@@ -329,7 +298,7 @@ static int switchdev_port_obj_del_now(struct net_device *dev,
 				      const struct switchdev_obj *obj)
 {
 	return switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_DEL,
-					 dev, obj, NULL, NULL);
+					 dev, obj, NULL);
 }
 
 static void switchdev_port_obj_del_deferred(struct net_device *dev,
@@ -449,7 +418,6 @@ static int __switchdev_handle_port_obj_add(struct net_device *dev,
 			bool (*check_cb)(const struct net_device *dev),
 			int (*add_cb)(struct net_device *dev,
 				      const struct switchdev_obj *obj,
-				      struct switchdev_trans *trans,
 				      struct netlink_ext_ack *extack))
 {
 	struct netlink_ext_ack *extack;
@@ -462,8 +430,7 @@ static int __switchdev_handle_port_obj_add(struct net_device *dev,
 	if (check_cb(dev)) {
 		/* This flag is only checked if the return value is success. */
 		port_obj_info->handled = true;
-		return add_cb(dev, port_obj_info->obj, port_obj_info->trans,
-			      extack);
+		return add_cb(dev, port_obj_info->obj, extack);
 	}
 
 	/* Switch ports might be stacked under e.g. a LAG. Ignore the
@@ -491,7 +458,6 @@ int switchdev_handle_port_obj_add(struct net_device *dev,
 			bool (*check_cb)(const struct net_device *dev),
 			int (*add_cb)(struct net_device *dev,
 				      const struct switchdev_obj *obj,
-				      struct switchdev_trans *trans,
 				      struct netlink_ext_ack *extack))
 {
 	int err;