spl: cmn_err_once() should be usable in brace-less if else statements

Commit 1191387 (openzfs#14567) added cmn_err_once() by #define'ing a
compound statement but failed to consider usage in a single
statement brace-less if else.

Fix the problem by using the common "do {} while (0)" construct.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes openzfs#14629

include/os/freebsd/spl/sys/cmn_err.h

@@ -75,36 +75,36 @@ extern void panic(const char *, ...)
     __attribute__((format(printf, 1, 2), __noreturn__));
 
 #define	cmn_err_once(ce, ...)				\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		cmn_err(ce, __VA_ARGS__);		\
 	}						\
-}
+} while (0)
 
 #define	vcmn_err_once(ce, fmt, ap)			\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		vcmn_err(ce, fmt, ap);			\
 	}						\
-}
+} while (0)
 
 #define	zcmn_err_once(zone, ce, ...)			\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		zcmn_err(zone, ce, __VA_ARGS__);	\
 	}						\
-}
+} while (0)
 
 #define	vzcmn_err_once(zone, ce, fmt, ap)		\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		vzcmn_err(zone, ce, fmt, ap);		\
 	}						\
-}
+} while (0)
 
 #endif /* !_ASM */
 

include/os/linux/spl/sys/cmn_err.h

@@ -47,19 +47,19 @@ extern void vpanic(const char *, va_list)
 #define	fm_panic	panic
 
 #define	cmn_err_once(ce, ...)				\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		cmn_err(ce, __VA_ARGS__);		\
 	}						\
-}
+} while (0)
 
 #define	vcmn_err_once(ce, fmt, ap)			\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		vcmn_err(ce, fmt, ap);			\
 	}						\
-}
+} while (0)
 
 #endif /* SPL_CMN_ERR_H */

lib/libspl/include/sys/cmn_err.h

@@ -30,35 +30,35 @@
 #include <atomic.h>
 
 #define	cmn_err_once(ce, ...)				\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		cmn_err(ce, __VA_ARGS__);		\
 	}						\
-}
+} while (0)
 
 #define	vcmn_err_once(ce, fmt, ap)			\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		vcmn_err(ce, fmt, ap);			\
 	}						\
-}
+} while (0)
 
 #define	zcmn_err_once(zone, ce, ...)			\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		zcmn_err(zone, ce, __VA_ARGS__);	\
 	}						\
-}
+} while (0)
 
 #define	vzcmn_err_once(zone, ce, fmt, ap)		\
-{							\
+do {							\
 	static volatile uint32_t printed = 0;		\
 	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
 		vzcmn_err(zone, ce, fmt, ap);		\
 	}						\
-}
+} while (0)
 
 #endif