The recently added test innodb.innodb_wl6326 hangs in 10.4, because a query

SELECT a00,a01 FROM t1 WHERE a00 = 'cp';

causes ha_innobase::records_in_range() to be called with min_key=NULL. No secondary indexes have been defined on the table; only PRIMARY KEY(a00,a01,a02,a03,a04,a05,a06).

That section of the test is demonstrating that only some pages of the table are supposed to be latched.

The hang is caused by ‘too broad’ ha_innobase::records_in_range() calls. Those calls were introduced by an early commit of MDEV-16188. With the parent of that commit, the following test will not hang:

git checkout bc43bf3e430c20bc2178e584215bd443054709d6 mysql-test/suite/innodb/t/innodb_wl6326.*

(cd path/to/build/mysql-test; ./mtr innodb.innodb_wl6326)

I would expect the too broad ha_innobase::records_in_range() calls to cause a performance regression, especially if they are being invoked for each and every query. InnoDB will not cache the results of that call in any way.