spl: Add cmn_err_once() to log a message only on the first call

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes #14567

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

@@ -29,6 +29,7 @@
 #else
 #include <stdarg.h>
 #endif
+#include <sys/atomic.h>
 
 #define	CE_CONT		0 /* continuation */
 #define	CE_NOTE		1 /* notice */
@@ -45,4 +46,20 @@ extern void vpanic(const char *, va_list)
 
 #define	fm_panic	panic
 
+#define	cmn_err_once(ce, ...)				\
+{							\
+	static volatile uint32_t printed = 0;		\
+	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
+		cmn_err(ce, __VA_ARGS__);		\
+	}						\
+}
+
+#define	vcmn_err_once(ce, fmt, ap)			\
+{							\
+	static volatile uint32_t printed = 0;		\
+	if (atomic_cas_32(&printed, 0, 1) == 0) {	\
+		vcmn_err(ce, fmt, ap);			\
+	}						\
+}
+
 #endif /* SPL_CMN_ERR_H */