Function dbuf_free_range

freebsd/contrib/openzfs/module/zfs/dbuf.c:1787–1886

* Evict (if its unreferenced) or clear (if its referenced) any level-0 * data blocks in the free range, so that any future readers will find * empty blocks. */

 * empty blocks.
 */
void
dbuf_free_range(dnode_t *dn, uint64_t start_blkid, uint64_t end_blkid,
    dmu_tx_t *tx)
{
	dmu_buf_impl_t *db_search;
	dmu_buf_impl_t *db, *db_next;
	uint64_t txg = tx->tx_txg;
	avl_index_t where;
	dbuf_dirty_record_t *dr;

	if (end_blkid > dn->dn_maxblkid &&
	    !(start_blkid == DMU_SPILL_BLKID || end_blkid == DMU_SPILL_BLKID))
		end_blkid = dn->dn_maxblkid;
	dprintf_dnode(dn, "start=%llu end=%llu\n", start_blkid, end_blkid);

	db_search = kmem_alloc(sizeof (dmu_buf_impl_t), KM_SLEEP);
	db_search->db_level = 0;
	db_search->db_blkid = start_blkid;
	db_search->db_state = DB_SEARCH;

	mutex_enter(&dn->dn_dbufs_mtx);
	db = avl_find(&dn->dn_dbufs, db_search, &where);
	ASSERT3P(db, ==, NULL);

	db = avl_nearest(&dn->dn_dbufs, where, AVL_AFTER);

	for (; db != NULL; db = db_next) {
		db_next = AVL_NEXT(&dn->dn_dbufs, db);
		ASSERT(db->db_blkid != DMU_BONUS_BLKID);

		if (db->db_level != 0 || db->db_blkid > end_blkid) {
			break;
		}
		ASSERT3U(db->db_blkid, >=, start_blkid);

		/* found a level 0 buffer in the range */
		mutex_enter(&db->db_mtx);
		if (dbuf_undirty(db, tx)) {
			/* mutex has been dropped and dbuf destroyed */
			continue;
		}

		if (db->db_state == DB_UNCACHED ||
		    db->db_state == DB_NOFILL ||
		    db->db_state == DB_EVICTING) {
			ASSERT(db->db.db_data == NULL);
			mutex_exit(&db->db_mtx);
			continue;
		}
		if (db->db_state == DB_READ || db->db_state == DB_FILL) {
			/* will be handled in dbuf_read_done or dbuf_rele */
			db->db_freed_in_flight = TRUE;
			mutex_exit(&db->db_mtx);
			continue;
		}
		if (zfs_refcount_count(&db->db_holds) == 0) {
			ASSERT(db->db_buf);
			dbuf_destroy(db);