devlink: add function to take snapshot while locked

A future change is going to add a new devlink command to request
a snapshot on demand. This function will want to call the
devlink_region_snapshot_create function while already holding the
devlink instance lock.

Extract the logic of this function into a static function prefixed by
`__` to indicate that it is an internal helper function. Modify the
original function to be implemented in terms of the new locked
function.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/devlink.c

@@ -3768,6 +3768,52 @@ static void devlink_nl_region_notify(struct devlink_region *region,
 	nlmsg_free(msg);
 }
 
+/**
+ *	__devlink_region_snapshot_create - create a new snapshot
+ *	This will add a new snapshot of a region. The snapshot
+ *	will be stored on the region struct and can be accessed
+ *	from devlink. This is useful for future analyses of snapshots.
+ *	Multiple snapshots can be created on a region.
+ *	The @snapshot_id should be obtained using the getter function.
+ *
+ *	Must be called only while holding the devlink instance lock.
+ *
+ *	@region: devlink region of the snapshot
+ *	@data: snapshot data
+ *	@snapshot_id: snapshot id to be created
+ */
+static int
+__devlink_region_snapshot_create(struct devlink_region *region,
+				 u8 *data, u32 snapshot_id)
+{
+	struct devlink *devlink = region->devlink;
+	struct devlink_snapshot *snapshot;
+
+	lockdep_assert_held(&devlink->lock);
+
+	/* check if region can hold one more snapshot */
+	if (region->cur_snapshots == region->max_snapshots)
+		return -ENOMEM;
+
+	if (devlink_region_snapshot_get_by_id(region, snapshot_id))
+		return -EEXIST;
+
+	snapshot = kzalloc(sizeof(*snapshot), GFP_KERNEL);
+	if (!snapshot)
+		return -ENOMEM;
+
+	snapshot->id = snapshot_id;
+	snapshot->region = region;
+	snapshot->data = data;
+
+	list_add_tail(&snapshot->list, &region->snapshot_list);
+
+	region->cur_snapshots++;
+
+	devlink_nl_region_notify(region, snapshot, DEVLINK_CMD_REGION_NEW);
+	return 0;
+}
+
 static void devlink_region_snapshot_del(struct devlink_region *region,
 					struct devlink_snapshot *snapshot)
 {
@@ -7753,42 +7799,12 @@ int devlink_region_snapshot_create(struct devlink_region *region,
 				   u8 *data, u32 snapshot_id)
 {
 	struct devlink *devlink = region->devlink;
-	struct devlink_snapshot *snapshot;
 	int err;
 
 	mutex_lock(&devlink->lock);
-
-	/* check if region can hold one more snapshot */
-	if (region->cur_snapshots == region->max_snapshots) {
-		err = -ENOMEM;
-		goto unlock;
-	}
-
-	if (devlink_region_snapshot_get_by_id(region, snapshot_id)) {
-		err = -EEXIST;
-		goto unlock;
-	}
-
-	snapshot = kzalloc(sizeof(*snapshot), GFP_KERNEL);
-	if (!snapshot) {
-		err = -ENOMEM;
-		goto unlock;
-	}
-
-	snapshot->id = snapshot_id;
-	snapshot->region = region;
-	snapshot->data = data;
-
-	list_add_tail(&snapshot->list, &region->snapshot_list);
-
-	region->cur_snapshots++;
-
-	devlink_nl_region_notify(region, snapshot, DEVLINK_CMD_REGION_NEW);
+	err = __devlink_region_snapshot_create(region, data, snapshot_id);
 	mutex_unlock(&devlink->lock);
-	return 0;
 
-unlock:
-	mutex_unlock(&devlink->lock);
 	return err;
 }
 EXPORT_SYMBOL_GPL(devlink_region_snapshot_create);