netdevsim: support taking immediate snapshot via devlink

Implement the .snapshot region operation for the dummy data region. This
enables a region snapshot to be taken upon request via the new
DEVLINK_CMD_REGION_SNAPSHOT command.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/dev.c

@@ -39,23 +39,38 @@ static struct dentry *nsim_dev_ddir;
 
 #define NSIM_DEV_DUMMY_REGION_SIZE (1024 * 32)
 
+static int
+nsim_dev_take_snapshot(struct devlink *devlink, struct netlink_ext_ack *extack,
+		       u8 **data)
+{
+	void *dummy_data;
+
+	dummy_data = kmalloc(NSIM_DEV_DUMMY_REGION_SIZE, GFP_KERNEL);
+	if (!dummy_data)
+		return -ENOMEM;
+
+	get_random_bytes(dummy_data, NSIM_DEV_DUMMY_REGION_SIZE);
+
+	*data = dummy_data;
+
+	return 0;
+}
+
 static ssize_t nsim_dev_take_snapshot_write(struct file *file,
 					    const char __user *data,
 					    size_t count, loff_t *ppos)
 {
 	struct nsim_dev *nsim_dev = file->private_data;
 	struct devlink *devlink;
-	void *dummy_data;
+	u8 *dummy_data;
 	int err;
 	u32 id;
 
 	devlink = priv_to_devlink(nsim_dev);
 
-	dummy_data = kmalloc(NSIM_DEV_DUMMY_REGION_SIZE, GFP_KERNEL);
-	if (!dummy_data)
-		return -ENOMEM;
-
-	get_random_bytes(dummy_data, NSIM_DEV_DUMMY_REGION_SIZE);
+	err = nsim_dev_take_snapshot(devlink, NULL, &dummy_data);
+	if (err)
+		return err;
 
 	err = devlink_region_snapshot_id_get(devlink, &id);
 	if (err) {
@@ -351,6 +366,7 @@ static void nsim_devlink_param_load_driverinit_values(struct devlink *devlink)
 static const struct devlink_region_ops dummy_region_ops = {
 	.name = "dummy",
 	.destructor = &kfree,
+	.snapshot = nsim_dev_take_snapshot,
 };
 
 static int nsim_dev_dummy_region_init(struct nsim_dev *nsim_dev,

tools/testing/selftests/drivers/net/netdevsim/devlink.sh

@@ -141,6 +141,16 @@ regions_test()
 
 	check_region_snapshot_count dummy post-first-delete 2
 
+	devlink region new $DL_HANDLE/dummy snapshot 25
+	check_err $? "Failed to create a new snapshot with id 25"
+
+	check_region_snapshot_count dummy post-first-request 3
+
+	devlink region del $DL_HANDLE/dummy snapshot 25
+	check_err $? "Failed to delete snapshot with id 25"
+
+	check_region_snapshot_count dummy post-second-delete 2
+
 	log_test "regions test"
 }