MDEV-24333 Data race in os_file_pread at os/os0file.cc:3308 on os_n_file_reads

os_n_file_reads: make Atomic_counter and correct the semantics of an imprecise
counter.

Reviewed by: Marko Mäkelä

storage/innobase/include/os0file.h

@@ -45,6 +45,8 @@ Created 10/21/1995 Heikki Tuuri
 #include <time.h>
 #endif /* !_WIN32 */
 
+#include "my_counter.h"
+
 /** File node of a tablespace or the log data space */
 struct fil_node_t;
 struct fil_space_t;
@@ -460,7 +462,7 @@ or write, causing a bottleneck for parallelism. */
 static const ulint OS_AIO_SYNC = 24;
 /* @} */
 
-extern ulint	os_n_file_reads;
+extern Atomic_counter<ulint> os_n_file_reads;
 extern ulint	os_n_file_writes;
 extern ulint	os_n_fsyncs;
 

storage/innobase/os/os0file.cc

@@ -674,7 +674,7 @@ static ulint		os_aio_n_segments = ULINT_UNDEFINED;
 wait until a batch of new read requests have been posted */
 static bool		os_aio_recommend_sleep_for_read_threads;
 
-ulint	os_n_file_reads;
+Atomic_counter<ulint> os_n_file_reads;
 static ulint	os_bytes_read_since_printout;
 ulint	os_n_file_writes;
 ulint	os_n_fsyncs;
@@ -7411,7 +7411,7 @@ os_aio_print(FILE*	file)
 		ULINTPF " OS fsyncs\n",
 		fil_n_pending_log_flushes,
 		fil_n_pending_tablespace_flushes,
-		os_n_file_reads,
+		ulint{os_n_file_reads},
 		os_n_file_writes,
 		os_n_fsyncs);