Re: [dm-devel] [PATCH v2 26/29] libmultipath: simplify dlog()

[Benjamin Marzinski <bmarzins@redhat.com>]

On Fri, Oct 16, 2020 at 12:44:58PM +0200, mwilck@suse.com wrote:
> From: Martin Wilck <mwilck@suse.com>
> 
> By checking the log level in condlog() directly, we can simplify
> dlog(). Also, it's now possible to limit the log level at compile
> time by setting MAX_VERBOSITY, enabling the compiler to optimize
> away log messages with higher loglevel.
> 
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
> Signed-off-by: Martin Wilck <mwilck@suse.com>
> ---
>  libmultipath/debug.c     | 30 +++++++++++++-----------------
>  libmultipath/debug.h     | 19 +++++++++++++++----
>  libmultipath/devmapper.c |  4 +++-
>  tests/test-log.c         |  4 ++--
>  tests/test-log.h         |  3 ++-
>  5 files changed, 35 insertions(+), 25 deletions(-)
> 
> diff --git a/libmultipath/debug.c b/libmultipath/debug.c
> index f9b7755..429f269 100644
> --- a/libmultipath/debug.c
> +++ b/libmultipath/debug.c
> @@ -18,29 +18,25 @@
>  int logsink;
>  int libmp_verbosity = DEFAULT_VERBOSITY;
>  
> -void dlog (int sink, int prio, const char * fmt, ...)
> +void dlog(int prio, const char * fmt, ...)
>  {
>  	va_list ap;
>  
>  	va_start(ap, fmt);
> +	if (logsink != LOGSINK_SYSLOG) {
> +		if (logsink == LOGSINK_STDERR_WITH_TIME) {
> +			time_t t = time(NULL);
> +			struct tm *tb = localtime(&t);
> +			char buff[16];
>  
> -	if (prio <= libmp_verbosity) {
> -		if (sink != LOGSINK_SYSLOG) {
> -			if (sink == LOGSINK_STDERR_WITH_TIME) {
> -				time_t t = time(NULL);
> -				struct tm *tb = localtime(&t);
> -				char buff[16];
> -
> -				strftime(buff, sizeof(buff),
> -					 "%b %d %H:%M:%S", tb);
> -				buff[sizeof(buff)-1] = '\0';
> -
> -				fprintf(stderr, "%s | ", buff);
> -			}
> -			vfprintf(stderr, fmt, ap);
> +			strftime(buff, sizeof(buff),
> +				 "%b %d %H:%M:%S", tb);
> +			buff[sizeof(buff)-1] = '\0';
> +			fprintf(stderr, "%s | ", buff);
>  		}
> -		else
> -			log_safe(prio + 3, fmt, ap);
> +		vfprintf(stderr, fmt, ap);
>  	}
> +	else
> +		log_safe(prio + 3, fmt, ap);
>  	va_end(ap);
>  }
> diff --git a/libmultipath/debug.h b/libmultipath/debug.h
> index 91ba02b..705a5d7 100644
> --- a/libmultipath/debug.h
> +++ b/libmultipath/debug.h
> @@ -1,5 +1,7 @@
> -void dlog (int sink, int prio, const char * fmt, ...)
> -	__attribute__((format(printf, 3, 4)));
> +#ifndef _DEBUG_H
> +#define _DEBUG_H
> +void dlog (int prio, const char *fmt, ...)
> +	__attribute__((format(printf, 2, 3)));
>  
>  
>  #include <pthread.h>
> @@ -10,8 +12,9 @@ void dlog (int sink, int prio, const char * fmt, ...)
>  extern int logsink;
>  extern int libmp_verbosity;
>  
> -#define condlog(prio, fmt, args...) \
> -	dlog(logsink, prio, fmt "\n", ##args)
> +#ifndef MAX_VERBOSITY
> +#define MAX_VERBOSITY 4
> +#endif
>  
>  enum {
>  	LOGSINK_STDERR_WITH_TIME = 0,
> @@ -19,3 +22,11 @@ enum {
>  	LOGSINK_SYSLOG = 1,
>  };
>  
> +#define condlog(prio, fmt, args...)					\
> +	do {								\
> +		int __p = (prio);					\
> +									\
> +		if (__p <= MAX_VERBOSITY && __p <= libmp_verbosity)	\
> +			dlog(__p, fmt "\n", ##args);			\
> +	} while (0)
> +#endif /* _DEBUG_H */
> diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
> index 78112a9..cf2f27c 100644
> --- a/libmultipath/devmapper.c
> +++ b/libmultipath/devmapper.c
> @@ -274,7 +274,9 @@ static int dm_tgt_prereq (unsigned int *ver)
>  
>  static void _init_versions(void)
>  {
> -	dlog(logsink, 3, VERSION_STRING);
> +	/* Can't use condlog here because of how VERSION_STRING is defined */
> +	if (3 <= libmp_verbosity)
> +		dlog(3, VERSION_STRING);
>  	init_dm_library_version();
>  	init_dm_drv_version();
>  	init_dm_mpath_version();
> diff --git a/tests/test-log.c b/tests/test-log.c
> index 051491e..42ebad0 100644
> --- a/tests/test-log.c
> +++ b/tests/test-log.c
> @@ -6,8 +6,8 @@
>  #include "log.h"
>  #include "test-log.h"
>  
> -__attribute__((format(printf, 3, 0)))
> -void __wrap_dlog (int sink, int prio, const char * fmt, ...)
> +__attribute__((format(printf, 2, 0)))
> +void __wrap_dlog (int prio, const char * fmt, ...)
>  {
>  	char buff[MAX_MSG_SIZE];
>  	va_list ap;
> diff --git a/tests/test-log.h b/tests/test-log.h
> index 2c878c6..6d22cd2 100644
> --- a/tests/test-log.h
> +++ b/tests/test-log.h
> @@ -1,7 +1,8 @@
>  #ifndef _TEST_LOG_H
>  #define _TEST_LOG_H
>  
> -void __wrap_dlog (int sink, int prio, const char * fmt, ...);
> +__attribute__((format(printf, 2, 0)))
> +void __wrap_dlog (int prio, const char * fmt, ...);
>  void expect_condlog(int prio, char *string);
>  
>  #endif
> -- 
> 2.28.0

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