Re: [PATCH v2 4/7] perf pmu: Add function to check if a pmu file exists

[Leo Yan]

On Thu, Dec 22, 2022 at 04:03:24PM +0000, James Clark wrote:
> From: German Gomez <german.gomez@xxxxxxx>
> 
> Add a utility function perf_pmu__file_exists() to check if a given pmu
> file exists in the sysfs filesystem.
> 
> Signed-off-by: German Gomez <german.gomez@xxxxxxx>
> Signed-off-by: James Clark <james.clark@xxxxxxx>
> ---
>  tools/perf/util/pmu.c | 14 ++++++++++++++
>  tools/perf/util/pmu.h |  2 ++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 15b852b3c401..b72b2d892949 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -1739,6 +1739,20 @@ int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
>  	return ret;
>  }
>  
> +bool perf_pmu__file_exists(struct perf_pmu *pmu, const char *name)
> +{
> +	char path[PATH_MAX];
> +	struct stat statbuf;
> +
> +	if (!perf_pmu__pathname_scnprintf(path, PATH_MAX, pmu->name, name))
> +		return false;
> +
> +	if (!file_available(path))
> +		return false;
> +
> +	return stat(path, &statbuf) == 0;

Can we simply return the returned value from file_available() and skip
calling stat()?  Because file_available() invokes access() to detect if
a file is existed or not, so here calling stat() is redundant.

Thanks,
Leo

> +}
> +
>  static int perf_pmu__new_caps(struct list_head *list, char *name, char *value)
>  {
>  	struct perf_pmu_caps *caps = zalloc(sizeof(*caps));
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index 8f39e2d17fb1..c1d138fe9602 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -230,6 +230,8 @@ bool pmu_have_event(const char *pname, const char *name);
>  
>  int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt, ...) __scanf(3, 4);
>  
> +bool perf_pmu__file_exists(struct perf_pmu *pmu, const char *name);
> +
>  int perf_pmu__test(void);
>  
>  struct perf_event_attr *perf_pmu__get_default_config(struct perf_pmu *pmu);
> -- 
> 2.25.1
>