f2fs_room_for_filename
bit_pos = f2fs_room_for_filename(d.bitmap, slots, d.max);
bit_pos = f2fs_room_for_filename(&dentry_blk->dentry_bitmap,
int f2fs_room_for_filename(const void *bitmap, int slots, int max_slots);
bit_pos = f2fs_room_for_filename(d.bitmap, slots, d.max);