once: implement DO_ONCE_LITE for non-fast-path "do once" functionality

Certain uses of "do once" functionality reside outside of fast path,
and so do not require jump label patching via static keys, making
existing DO_ONCE undesirable in such cases.

Replace uses of __section(".data.once") with DO_ONCE_LITE(_IF)?

This patch changes the return values of xfs_printk_once, printk_once,
and printk_deferred_once. Before, they returned whether the print was
performed, but now, they always return true. This is okay because the
return values of the following macros are entirely ignored throughout
the kernel:
- xfs_printk_once
- xfs_warn_once
- xfs_notice_once
- xfs_info_once
- printk_once
- pr_emerg_once
- pr_alert_once
- pr_crit_once
- pr_err_once
- pr_warn_once
- pr_notice_once
- pr_info_once
- pr_devel_once
- pr_debug_once
- printk_deferred_once
- orc_warn

Changes
v3:
  - Expand commit message to explain why changing return values of
    xfs_printk_once, printk_once, printk_deferred_once is benign
v2:
  - Fix i386 build warnings

Signed-off-by: Tanner Love <tannerlove@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Mahesh Bandewar <maheshb@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/xfs/xfs_message.h

@@ -2,6 +2,8 @@
 #ifndef __XFS_MESSAGE_H
 #define __XFS_MESSAGE_H 1
 
+#include <linux/once_lite.h>
+
 struct xfs_mount;
 
 extern __printf(2, 3)
@@ -41,16 +43,7 @@ do {									\
 } while (0)
 
 #define xfs_printk_once(func, dev, fmt, ...)			\
-({								\
+	DO_ONCE_LITE(func, dev, fmt, ##__VA_ARGS__)
-	static bool __section(".data.once") __print_once;	\
-	bool __ret_print_once = !__print_once; 			\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		func(dev, fmt, ##__VA_ARGS__);			\
-	}							\
-	unlikely(__ret_print_once);				\
-})
 
 #define xfs_emerg_ratelimited(dev, fmt, ...)				\
 	xfs_printk_ratelimited(xfs_emerg, dev, fmt, ##__VA_ARGS__)

include/asm-generic/bug.h

@@ -4,6 +4,7 @@
 
 #include <linux/compiler.h>
 #include <linux/instrumentation.h>
+#include <linux/once_lite.h>
 
 #define CUT_HERE		"------------[ cut here ]------------\n"
 
@@ -140,39 +141,15 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 })
 
 #ifndef WARN_ON_ONCE
-#define WARN_ON_ONCE(condition)	({				\
+#define WARN_ON_ONCE(condition)					\
-	static bool __section(".data.once") __warned;		\
+	DO_ONCE_LITE_IF(condition, WARN_ON, 1)
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		WARN_ON(1);					\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
 #endif
 
-#define WARN_ONCE(condition, format...)	({			\
+#define WARN_ONCE(condition, format...)				\
-	static bool __section(".data.once") __warned;		\
+	DO_ONCE_LITE_IF(condition, WARN, 1, format)
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		WARN(1, format);				\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
 
-#define WARN_TAINT_ONCE(condition, taint, format...)	({	\
+#define WARN_TAINT_ONCE(condition, taint, format...)		\
-	static bool __section(".data.once") __warned;		\
+	DO_ONCE_LITE_IF(condition, WARN_TAINT, 1, taint, format)
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		WARN_TAINT(1, taint, format);			\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
 
 #else /* !CONFIG_BUG */
 #ifndef HAVE_ARCH_BUG

include/linux/once_lite.h

@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ONCE_LITE_H
+#define _LINUX_ONCE_LITE_H
+
+#include <linux/types.h>
+
+/* Call a function once. Similar to DO_ONCE(), but does not use jump label
+ * patching via static keys.
+ */
+#define DO_ONCE_LITE(func, ...)						\
+	DO_ONCE_LITE_IF(true, func, ##__VA_ARGS__)
+#define DO_ONCE_LITE_IF(condition, func, ...)				\
+	({								\
+		static bool __section(".data.once") __already_done;	\
+		bool __ret_do_once = !!(condition);			\
+									\
+		if (unlikely(__ret_do_once && !__already_done)) {	\
+			__already_done = true;				\
+			func(__VA_ARGS__);				\
+		}							\
+		unlikely(__ret_do_once);				\
+	})
+
+#endif /* _LINUX_ONCE_LITE_H */

include/linux/printk.h

@@ -8,6 +8,7 @@
 #include <linux/linkage.h>
 #include <linux/cache.h>
 #include <linux/ratelimit_types.h>
+#include <linux/once_lite.h>
 
 extern const char linux_banner[];
 extern const char linux_proc_banner[];
@@ -436,27 +437,9 @@ extern int kptr_restrict;
 
 #ifdef CONFIG_PRINTK
 #define printk_once(fmt, ...)					\
-({								\
+	DO_ONCE_LITE(printk, fmt, ##__VA_ARGS__)
-	static bool __section(".data.once") __print_once;	\
-	bool __ret_print_once = !__print_once;			\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		printk(fmt, ##__VA_ARGS__);			\
-	}							\
-	unlikely(__ret_print_once);				\
-})
 #define printk_deferred_once(fmt, ...)				\
-({								\
+	DO_ONCE_LITE(printk_deferred, fmt, ##__VA_ARGS__)
-	static bool __section(".data.once") __print_once;	\
-	bool __ret_print_once = !__print_once;			\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		printk_deferred(fmt, ##__VA_ARGS__);		\
-	}							\
-	unlikely(__ret_print_once);				\
-})
 #else
 #define printk_once(fmt, ...)					\
 	no_printk(fmt, ##__VA_ARGS__)

kernel/trace/trace.h

@@ -20,6 +20,7 @@
 #include <linux/irq_work.h>
 #include <linux/workqueue.h>
 #include <linux/ctype.h>
+#include <linux/once_lite.h>
 
 #ifdef CONFIG_FTRACE_SYSCALLS
 #include <asm/unistd.h>		/* For NR_SYSCALLS	     */
@@ -99,16 +100,8 @@ enum trace_type {
 #include "trace_entries.h"
 
 /* Use this for memory failure errors */
-#define MEM_FAIL(condition, fmt, ...) ({			\
+#define MEM_FAIL(condition, fmt, ...)					\
-	static bool __section(".data.once") __warned;		\
+	DO_ONCE_LITE_IF(condition, pr_err, "ERROR: " fmt, ##__VA_ARGS__)
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		pr_err("ERROR: " fmt, ##__VA_ARGS__);		\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
 
 /*
  * syscalls are special, and need special handling, this is why