linux-kernel - [RFC][PATCH v1 1/1] Add WARN_ONCE

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Date:	Fri, 14 Aug 2015 16:43:19 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Arnd Bergmann <arnd@...db.de>,
	Casey Schaufler <casey@...aufler-ca.com>,
	linux-kernel@...r.kernel.org
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [RFC][PATCH v1 1/1] Add WARN_ONCE_RETURN macro

The rationale is to replace the
	if (condition) {
		WARN_ONCE(1, ...);
		return value;
	}
by
	WARN_ONCE_RETURN(condition, value, ...);

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 include/asm-generic/bug.h  | 17 +++++++++++++++++
 security/smack/smack_lsm.c |  5 +----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 630dd23..fbf20fd 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -126,6 +126,18 @@ extern void warn_slowpath_null(const char *file, const int line);
 	unlikely(__ret_warn_once);				\
 })
 
+#define WARN_ONCE_RETURN(condition, value, format...)		\
+do {								\
+	static bool __section(.data.unlikely) __warned;		\
+	int __ret_warn_once = !!(condition);			\
+								\
+	if (unlikely(__ret_warn_once)) {			\
+		if (WARN(!__warned, format)) 			\
+			__warned = true;			\
+		return value;					\
+	}							\
+} while (0)
+
 #define WARN_TAINT_ONCE(condition, taint, format...)	({	\
 	static bool __section(.data.unlikely) __warned;		\
 	int __ret_warn_once = !!(condition);			\
@@ -162,6 +174,11 @@ extern void warn_slowpath_null(const char *file, const int line);
 
 #define WARN_ON_ONCE(condition) WARN_ON(condition)
 #define WARN_ONCE(condition, format...) WARN(condition, format)
+#define WARN_ONCE_RETURN(condition, value, format...)			\
+do {									\
+	if (WARN(condition, format))					\
+		return value;						\
+} while (0)
 #define WARN_TAINT(condition, taint, format...) WARN(condition, format)
 #define WARN_TAINT_ONCE(condition, taint, format...) WARN(condition, format)
 
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 54fb3a1..4160d0e 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4401,10 +4401,7 @@ static int smack_audit_rule_match(u32 secid, u32 field, u32 op, void *vrule,
 	struct smack_known *skp;
 	char *rule = vrule;
 
-	if (unlikely(!rule)) {
-		WARN_ONCE(1, "Smack: missing rule\n");
-		return -ENOENT;
-	}
+	WARN_ONCE_RETURN(unlikely(!rule), -ENOENT, "Smack: missing rule\n");
 
 	if (field != AUDIT_SUBJ_USER && field != AUDIT_OBJ_USER)
 		return 0;
-- 
2.5.0

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