When InnoDB attempts to buffer a change operation of a secondary index
leaf page (to insert, delete-mark or remove a record) and the
change buffer is too large, InnoDB used to trigger a change buffer merge
that could affect any tables. This could lead to huge variance in
system throughput and potentially unpredictable crashes, in case the
change buffer was corrupted and a crash occurred while attempting to
merge changes to a table that is not being accessed by the current
SQL statement.

ibuf_insert_low(): Simply return DB_STRONG_FAIL when the maximum size
of the change buffer is exceeded.

ibuf_contract_after_insert(): Remove.

ibuf_get_merge_page_nos_func(): Remove a constant parameter.
The function ibuf_contract() will be our only caller, during
shutdown with innodb_fast_shutdown=0.