u64 new_dirid, u64 alloc_hint);
int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
size_t size, struct bio *bio, unsigned long bio_flags);
u64 new_dirid, u64 alloc_hint);
int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
size_t size, struct bio *bio, unsigned long bio_flags);