return 0;
 }
 
-static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
+static inline u32 free_space_bitmap_size(const struct btrfs_fs_info *fs_info,
+                                        u64 size)
 {
-       return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
+       return DIV_ROUND_UP(size >> fs_info->sectorsize_bits, BITS_PER_BYTE);
 }
 
 static unsigned long *alloc_bitmap(u32 bitmap_size)
        int done = 0, nr;
        int ret;
 
-       bitmap_size = free_space_bitmap_size(block_group->length,
-                                            fs_info->sectorsize);
+       bitmap_size = free_space_bitmap_size(fs_info, block_group->length);
        bitmap = alloc_bitmap(bitmap_size);
        if (!bitmap) {
                ret = -ENOMEM;
                u32 data_size;
 
                extent_size = min(end - i, bitmap_range);
-               data_size = free_space_bitmap_size(extent_size,
-                                                  fs_info->sectorsize);
+               data_size = free_space_bitmap_size(fs_info, extent_size);
 
                key.objectid = i;
                key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
        int done = 0, nr;
        int ret;
 
-       bitmap_size = free_space_bitmap_size(block_group->length,
-                                            fs_info->sectorsize);
+       bitmap_size = free_space_bitmap_size(fs_info, block_group->length);
        bitmap = alloc_bitmap(bitmap_size);
        if (!bitmap) {
                ret = -ENOMEM;
                                                     fs_info->sectorsize *
                                                     BITS_PER_BYTE);
                                bitmap_cursor = ((char *)bitmap) + bitmap_pos;
-                               data_size = free_space_bitmap_size(found_key.offset,
-                                                                  fs_info->sectorsize);
+                               data_size = free_space_bitmap_size(fs_info,
+                                                               found_key.offset);
 
                                ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
                                read_extent_buffer(leaf, bitmap_cursor, ptr,