MDEV-17441 - InnoDB transition to C++11 atomics

btr_defragment_compression_failures, btr_defragment_failures and
btr_defragment_count transition to Atomic_counter.

storage/innobase/btr/btr0defragment.cc

@@ -63,14 +63,14 @@ UNIV_INTERN mysql_pfs_key_t	btr_defragment_mutex_key;
 
 /* Number of compression failures caused by defragmentation since server
 start. */
-ulint btr_defragment_compression_failures = 0;
+Atomic_counter<ulint> btr_defragment_compression_failures;
 /* Number of btr_defragment_n_pages calls that altered page but didn't
 manage to release any page. */
-ulint btr_defragment_failures = 0;
+Atomic_counter<ulint> btr_defragment_failures;
 /* Total number of btr_defragment_n_pages calls that altered page.
 The difference between btr_defragment_count and btr_defragment_failures shows
 the amount of effort wasted. */
-ulint btr_defragment_count = 0;
+Atomic_counter<ulint> btr_defragment_count;
 
 /******************************************************************//**
 Constructor for btr_defragment_item_t. */
@@ -448,8 +448,7 @@ btr_defragment_merge_pages(
 		// n_recs_to_move number of records to to_page. We try to reduce
 		// the targeted data size on the to_page by
 		// BTR_DEFRAGMENT_PAGE_REDUCTION_STEP_SIZE and try again.
-		my_atomic_addlint(
-			&btr_defragment_compression_failures, 1);
+		btr_defragment_compression_failures++;
 		max_ins_size_to_use =
 			move_size > BTR_DEFRAGMENT_PAGE_REDUCTION_STEP_SIZE
 			? move_size - BTR_DEFRAGMENT_PAGE_REDUCTION_STEP_SIZE
@@ -668,11 +667,9 @@ btr_defragment_n_pages(
 	}
 	mem_heap_free(heap);
 	n_defragmented ++;
-	my_atomic_addlint(
-		&btr_defragment_count, 1);
+	btr_defragment_count++;
 	if (n_pages == n_defragmented) {
-		my_atomic_addlint(
-			&btr_defragment_failures, 1);
+		btr_defragment_failures++;
 	} else {
 		index->stat_defrag_n_pages_freed += (n_pages - n_defragmented);
 	}

storage/innobase/include/btr0defragment.h

@@ -26,9 +26,9 @@ this program; if not, write to the Free Software Foundation, Inc.,
 #define BTR_DEFRAGMENT_MAX_N_PAGES	32
 
 /** stats in btr_defragment */
-extern ulint btr_defragment_compression_failures;
-extern ulint btr_defragment_failures;
-extern ulint btr_defragment_count;
+extern Atomic_counter<ulint> btr_defragment_compression_failures;
+extern Atomic_counter<ulint> btr_defragment_failures;
+extern Atomic_counter<ulint> btr_defragment_count;
 
 /** Item in the work queue for btr_degrament_thread. */
 struct btr_defragment_item_t