opcache: Use O_TMPFILE file lock if available (#8634)

Use O_TMPFILE if the kernel supports it to create the lock fd, this
has multiple advantages including not having to worry about naming,
permissions and the assurance that it will always go away cleanly
even on abnormal termination.

Co-authored-by: Dmitry Stogov <[email protected]>

Author: crrodriguez

ext/opcache/zend_shared_alloc.c

@@ -100,6 +100,15 @@ void zend_shared_alloc_create_lock(char *lockfile_path)
 		return;
 #endif
 
+#ifdef O_TMPFILE
+	lock_file = open(lockfile_path, O_RDWR | O_TMPFILE | O_EXCL | O_CLOEXEC, 0666);
+	/* lack of O_TMPFILE support results in many possible errors
+	 * use it only when open returns a non-negative integer */
+	if (lock_file >= 0) {
+		return;
+	}
+#endif
+
 	snprintf(lockfile_name, sizeof(lockfile_name), "%s/%sXXXXXX", lockfile_path, SEM_FILENAME_PREFIX);
 	lock_file = mkstemp(lockfile_name);
 	if (lock_file == -1) {