MDEV-23966 btr_search_sys->hash_tables accessed without taking proper ahi latch

This issue is caused by the commit af40a2b4.
In btr_search_update_hash_on_insert(), btr_search_sys->hash_tables
is being accessed without taking proper ahi latch. During buffer pool
resizing, btr_get_search_table() is being accessed and it leads to
segmentation fault.

Reviewed-by: Marko Mäkelä

storage/innobase/btr/btr0sea.cc

@@ -1797,7 +1797,8 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 	}
 
 	rw_lock_t* const latch = btr_get_search_latch(index);
-	hash_table_t* const table = btr_get_search_table(index);
+	/* We must not look up "table" before acquiring the latch. */
+	hash_table_t* table = NULL;
 	bool locked = false;
 
 	if (!page_rec_is_infimum(rec)) {
@@ -1814,6 +1815,7 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 				goto function_exit;
 			}
 
+			table = btr_get_search_table(index);
 			ha_insert_for_fold(table, ins_fold, block, ins_rec);
 		}
 
@@ -1829,6 +1831,8 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 			if (!btr_search_enabled || !block->index) {
 				goto function_exit;
 			}
+
+			table = btr_get_search_table(index);
 		}
 
 		if (!left_side) {
@@ -1849,6 +1853,8 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 				if (!btr_search_enabled || !block->index) {
 					goto function_exit;
 				}
+
+				table = btr_get_search_table(index);
 			}
 
 			ha_insert_for_fold(table, ins_fold, block, ins_rec);
@@ -1865,6 +1871,8 @@ btr_search_update_hash_on_insert(btr_cur_t* cursor)
 			if (!btr_search_enabled || !block->index) {
 				goto function_exit;
 			}
+
+			table = btr_get_search_table(index);
 		}
 
 		if (!left_side) {