btrfs: simplify setting/clearing fs_info to btrfs_fs_devices

It makes no sense to have sysfs-related routines be responsible for
properly initialising the fs_info pointer of struct btrfs_fs_device.
Instead this can be streamlined by making it the responsibility of
btrfs_init_devices_late to initialize it. That function already
initializes fs_info of every individual device in btrfs_fs_devices.

As far as clearing it is concerned it makes sense to move it to
close_fs_devices. That function is only called when struct
btrfs_fs_devices is no longer in use - either for holding seeds or
main devices for a mounted filesystem.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/sysfs.c

@@ -939,8 +939,6 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)
 {
 	struct kobject *fsid_kobj = &fs_info->fs_devices->fsid_kobj;
 
-	btrfs_reset_fs_info_ptr(fs_info);
-
 	sysfs_remove_link(fsid_kobj, "bdi");
 
 	if (fs_info->space_info_kobj) {
@@ -1404,8 +1402,6 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
 	struct btrfs_fs_devices *fs_devs = fs_info->fs_devices;
 	struct kobject *fsid_kobj = &fs_devs->fsid_kobj;
 
-	btrfs_set_fs_info_ptr(fs_info);
-
 	error = btrfs_sysfs_add_devices_dir(fs_devs, NULL);
 	if (error)
 		return error;

fs/btrfs/volumes.c

@@ -1173,6 +1173,7 @@ static void close_fs_devices(struct btrfs_fs_devices *fs_devices)
 	WARN_ON(fs_devices->rw_devices);
 	fs_devices->opened = 0;
 	fs_devices->seeding = false;
+	fs_devices->fs_info = NULL;
 }
 
 void btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
@@ -7201,6 +7202,7 @@ void btrfs_init_devices_late(struct btrfs_fs_info *fs_info)
 			device->fs_info = fs_info;
 		mutex_unlock(&fs_devices->device_list_mutex);
 
+		fs_devices->fs_info = fs_info;
 		fs_devices = fs_devices->seed;
 	}
 }
@@ -7499,24 +7501,6 @@ void btrfs_commit_device_sizes(struct btrfs_transaction *trans)
 	mutex_unlock(&trans->fs_info->chunk_mutex);
 }
 
-void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info)
-{
-	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	while (fs_devices) {
-		fs_devices->fs_info = fs_info;
-		fs_devices = fs_devices->seed;
-	}
-}
-
-void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info)
-{
-	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	while (fs_devices) {
-		fs_devices->fs_info = NULL;
-		fs_devices = fs_devices->seed;
-	}
-}
-
 /*
  * Multiplicity factor for simple profiles: DUP, RAID1-like and RAID10.
  */

fs/btrfs/volumes.h

@@ -569,8 +569,6 @@ static inline enum btrfs_raid_types btrfs_bg_flags_to_raid_index(u64 flags)
 void btrfs_commit_device_sizes(struct btrfs_transaction *trans);
 
 struct list_head * __attribute_const__ btrfs_get_fs_uuids(void);
-void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info);
-void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info);
 bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info,
 					struct btrfs_device *failing_dev);
 void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,