Function dbuf_check_blkptr

freebsd/contrib/openzfs/module/zfs/dbuf.c:3850–3893

}

static void
dbuf_check_blkptr(dnode_t *dn, dmu_buf_impl_t *db)
{
	/* ASSERT(dmu_tx_is_syncing(tx) */
	ASSERT(MUTEX_HELD(&db->db_mtx));

	if (db->db_blkptr != NULL)
		return;

	if (db->db_blkid == DMU_SPILL_BLKID) {
		db->db_blkptr = DN_SPILL_BLKPTR(dn->dn_phys);
		BP_ZERO(db->db_blkptr);
		return;
	}
	if (db->db_level == dn->dn_phys->dn_nlevels-1) {
		/*
		 * This buffer was allocated at a time when there was
		 * no available blkptrs from the dnode, or it was
		 * inappropriate to hook it in (i.e., nlevels mismatch).
		 */
		ASSERT(db->db_blkid < dn->dn_phys->dn_nblkptr);
		ASSERT(db->db_parent == NULL);
		db->db_parent = dn->dn_dbuf;
		db->db_blkptr = &dn->dn_phys->dn_blkptr[db->db_blkid];
		DBUF_VERIFY(db);
	} else {
		dmu_buf_impl_t *parent = db->db_parent;
		int epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;

		ASSERT(dn->dn_phys->dn_nlevels > 1);
		if (parent == NULL) {
			mutex_exit(&db->db_mtx);
			rw_enter(&dn->dn_struct_rwlock, RW_READER);
			parent = dbuf_hold_level(dn, db->db_level + 1,
			    db->db_blkid >> epbs, db);
			rw_exit(&dn->dn_struct_rwlock);
			mutex_enter(&db->db_mtx);
			db->db_parent = parent;
		}
		db->db_blkptr = (blkptr_t *)parent->db.db_data +
		    (db->db_blkid & ((1ULL << epbs) - 1));
		DBUF_VERIFY(db);
	}
}

static void
dbuf_sync_bonus(dbuf_dirty_record_t *dr, dmu_tx_t *tx)