btrfs: qgroup: Cleanup old inaccurate facilities

Cleanup the old facilities which use old btrfs_qgroup_reserve() function
call, replace them with the newer version, and remove the "__" prefix in
them.

Also, make btrfs_qgroup_reserve/free() functions private, as they are
now only used inside qgroup codes.

Now, the whole btrfs qgroup is swithed to use the new reserve facilities.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 29b3702..47785c8 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1529,7 +1529,7 @@
 				goto reserve_metadata;
 			}
 		}
-		ret = __btrfs_check_data_free_space(inode, pos, write_bytes);
+		ret = btrfs_check_data_free_space(inode, pos, write_bytes);
 		if (ret < 0)
 			break;
 
@@ -1537,8 +1537,8 @@
 		ret = btrfs_delalloc_reserve_metadata(inode, reserve_bytes);
 		if (ret) {
 			if (!only_release_metadata)
-				__btrfs_free_reserved_data_space(inode, pos,
-							         write_bytes);
+				btrfs_free_reserved_data_space(inode, pos,
+							       write_bytes);
 			else
 				btrfs_end_write_no_snapshoting(root);
 			break;
@@ -1608,7 +1608,7 @@
 				btrfs_delalloc_release_metadata(inode,
 								release_bytes);
 			else
-				__btrfs_delalloc_release_space(inode, pos,
+				btrfs_delalloc_release_space(inode, pos,
 							     release_bytes);
 		}
 
@@ -1661,8 +1661,7 @@
 			btrfs_end_write_no_snapshoting(root);
 			btrfs_delalloc_release_metadata(inode, release_bytes);
 		} else {
-			__btrfs_delalloc_release_space(inode, pos,
-						       release_bytes);
+			btrfs_delalloc_release_space(inode, pos, release_bytes);
 		}
 	}
 
@@ -2708,8 +2707,8 @@
 out:
 	mutex_unlock(&inode->i_mutex);
 	/* Let go of our reservation. */
-	__btrfs_free_reserved_data_space(inode, alloc_start,
-					 alloc_end - alloc_start);
+	btrfs_free_reserved_data_space(inode, alloc_start,
+				       alloc_end - alloc_start);
 	return ret;
 }