btrfs: make device scan less noisy

Print the message only when the device is seen for the first time.
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/volumes.c

@@ -448,6 +448,14 @@ static void pending_bios_fn(struct btrfs_work *work)
 	run_scheduled_bios(device);
 }
 
+/*
+ * Add new device to list of registered devices
+ *
+ * Returns:
+ * 1   - first time device is seen
+ * 0   - device already known
+ * < 0 - error
+ */
 static noinline int device_list_add(const char *path,
 			   struct btrfs_super_block *disk_super,
 			   u64 devid, struct btrfs_fs_devices **fs_devices_ret)
@@ -455,6 +463,7 @@ static noinline int device_list_add(const char *path,
 	struct btrfs_device *device;
 	struct btrfs_fs_devices *fs_devices;
 	struct rcu_string *name;
+	int ret = 0;
 	u64 found_transid = btrfs_super_generation(disk_super);
 
 	fs_devices = find_fsid(disk_super->fsid);
@@ -495,6 +504,7 @@ static noinline int device_list_add(const char *path,
 		fs_devices->num_devices++;
 		mutex_unlock(&fs_devices->device_list_mutex);
 
+		ret = 1;
 		device->fs_devices = fs_devices;
 	} else if (!device->name || strcmp(device->name->str, path)) {
 		name = rcu_string_strdup(path, GFP_NOFS);
@@ -513,7 +523,8 @@ static noinline int device_list_add(const char *path,
 		fs_devices->latest_trans = found_transid;
 	}
 	*fs_devices_ret = fs_devices;
-	return 0;
+
+	return ret;
 }
 
 static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
@@ -910,6 +921,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 	transid = btrfs_super_generation(disk_super);
 	total_devices = btrfs_super_num_devices(disk_super);
 
+	ret = device_list_add(path, disk_super, devid, fs_devices_ret);
+	if (ret > 0) {
 		if (disk_super->label[0]) {
 			if (disk_super->label[BTRFS_LABEL_SIZE - 1])
 				disk_super->label[BTRFS_LABEL_SIZE - 1] = '\0';
@@ -919,8 +932,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 		}
 
 		printk(KERN_CONT "devid %llu transid %llu %s\n", devid, transid, path);
-
-	ret = device_list_add(path, disk_super, devid, fs_devices_ret);
+		ret = 0;
+	}
 	if (!ret && fs_devices_ret)
 		(*fs_devices_ret)->total_devices = total_devices;