btrfs: cleanup helpers that reset balance state

The function __cancel_balance name is confusing with the cancel
operation of balance and it really resets the state of balance back to
zero. The unset_balance_control helper is called only from one place and
simple enough to be inlined.
Reviewed-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -4459,10 +4459,10 @@ static long btrfs_ioctl_balance(struct file *file, void __user *arg)
 
 do_balance:
 	/*
-	 * Ownership of bctl and filesystem flag BTRFS_FS_EXCL_OP
-	 * goes to to btrfs_balance.  bctl is freed in __cancel_balance,
-	 * or, if restriper was paused all the way until unmount, in
-	 * free_fs_info.  The flag should be cleared after __cancel_balance.
+	 * Ownership of bctl and filesystem flag BTRFS_FS_EXCL_OP goes to
+	 * btrfs_balance.  bctl is freed in reset_balance_state, or, if
+	 * restriper was paused all the way until unmount, in free_fs_info.
+	 * The flag should be cleared after reset_balance_state.
 	 */
 	need_unlock = false;
 

fs/btrfs/volumes.c

@@ -3212,7 +3212,7 @@ static void update_balance_args(struct btrfs_balance_control *bctl)
 /*
  * Should be called with both balance and volume mutexes held to
  * serialize other volume operations (add_dev/rm_dev/resize) with
- * restriper.  Same goes for unset_balance_control.
+ * restriper.  Same goes for reset_balance_state.
  */
 static void set_balance_control(struct btrfs_balance_control *bctl)
 {
@@ -3225,9 +3225,13 @@ static void set_balance_control(struct btrfs_balance_control *bctl)
 	spin_unlock(&fs_info->balance_lock);
 }
 
-static void unset_balance_control(struct btrfs_fs_info *fs_info)
+/*
+ * Clear the balance status in fs_info and delete the balance item from disk.
+ */
+static void reset_balance_state(struct btrfs_fs_info *fs_info)
 {
 	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
+	int ret;
 
 	BUG_ON(!fs_info->balance_ctl);
 
@@ -3236,6 +3240,9 @@ static void unset_balance_control(struct btrfs_fs_info *fs_info)
 	spin_unlock(&fs_info->balance_lock);
 
 	kfree(bctl);
+	ret = del_balance_item(fs_info);
+	if (ret)
+		btrfs_handle_fs_error(fs_info, ret, NULL);
 }
 
 /*
@@ -3772,16 +3779,6 @@ static inline int balance_need_close(struct btrfs_fs_info *fs_info)
 		 atomic_read(&fs_info->balance_cancel_req) == 0);
 }
 
-static void __cancel_balance(struct btrfs_fs_info *fs_info)
-{
-	int ret;
-
-	unset_balance_control(fs_info);
-	ret = del_balance_item(fs_info);
-	if (ret)
-		btrfs_handle_fs_error(fs_info, ret, NULL);
-}
-
 /* Non-zero return value signifies invalidity */
 static inline int validate_convert_profile(struct btrfs_balance_args *bctl_arg,
 		u64 allowed)
@@ -3936,7 +3933,7 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
 
 	if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
 	    balance_need_close(fs_info)) {
-		__cancel_balance(fs_info);
+		reset_balance_state(fs_info);
 		clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 	}
 
@@ -3945,7 +3942,7 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
 	return ret;
 out:
 	if (bctl->flags & BTRFS_BALANCE_RESUME)
-		__cancel_balance(fs_info);
+		reset_balance_state(fs_info);
 	else
 		kfree(bctl);
 	clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
@@ -4124,13 +4121,13 @@ int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
 			   atomic_read(&fs_info->balance_running) == 0);
 		mutex_lock(&fs_info->balance_mutex);
 	} else {
-		/* __cancel_balance needs volume_mutex */
+		/* reset_balance_state needs volume_mutex */
 		mutex_unlock(&fs_info->balance_mutex);
 		mutex_lock(&fs_info->volume_mutex);
 		mutex_lock(&fs_info->balance_mutex);
 
 		if (fs_info->balance_ctl) {
-			__cancel_balance(fs_info);
+			reset_balance_state(fs_info);
 			clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
 		}