Re: [PATCH v2] tools lib api fs: Move cgroupsfs__mountpoint()

[Jiri Olsa]

On Tue, Jan 28, 2020 at 09:49:40AM +0900, Namhyung Kim wrote:
> Move it from tools/perf/util/cgroup.c as it can be used by other places.
> Note that cgroup filesystem is different from others since it's usually
> mounted separately (in v1) for each subsystem.
> 
> I just copied the code with a little modification to pass a name of
> subsystem and renamed it to follow other APIs.
> 
> Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka

> ---
> * rename to cgroupfs__mountpoint()
> 
>  tools/lib/api/fs/Build    |  1 +
>  tools/lib/api/fs/cgroup.c | 67 +++++++++++++++++++++++++++++++++++++++
>  tools/lib/api/fs/fs.h     |  2 ++
>  tools/perf/util/cgroup.c  | 63 ++----------------------------------
>  4 files changed, 72 insertions(+), 61 deletions(-)
>  create mode 100644 tools/lib/api/fs/cgroup.c
> 
> diff --git a/tools/lib/api/fs/Build b/tools/lib/api/fs/Build
> index f4ed9629ae85..0f75b28654de 100644
> --- a/tools/lib/api/fs/Build
> +++ b/tools/lib/api/fs/Build
> @@ -1,2 +1,3 @@
>  libapi-y += fs.o
>  libapi-y += tracing_path.o
> +libapi-y += cgroup.o
> diff --git a/tools/lib/api/fs/cgroup.c b/tools/lib/api/fs/cgroup.c
> new file mode 100644
> index 000000000000..c7e1cdaa36e1
> --- /dev/null
> +++ b/tools/lib/api/fs/cgroup.c
> @@ -0,0 +1,67 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/stringify.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include "fs.h"
> +
> +int cgroupfs__mountpoint(char *buf, size_t maxlen, const char *subsys)
> +{
> +	FILE *fp;
> +	char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1];
> +	char path_v1[PATH_MAX + 1], path_v2[PATH_MAX + 2], *path;
> +	char *token, *saved_ptr = NULL;
> +
> +	fp = fopen("/proc/mounts", "r");
> +	if (!fp)
> +		return -1;
> +
> +	/*
> +	 * in order to handle split hierarchy, we need to scan /proc/mounts
> +	 * and inspect every cgroupfs mount point to find one that has
> +	 * perf_event subsystem
> +	 */
> +	path_v1[0] = '\0';
> +	path_v2[0] = '\0';
> +
> +	while (fscanf(fp, "%*s %"__stringify(PATH_MAX)"s %"__stringify(PATH_MAX)"s %"
> +				__stringify(PATH_MAX)"s %*d %*d\n",
> +				mountpoint, type, tokens) == 3) {
> +
> +		if (!path_v1[0] && !strcmp(type, "cgroup")) {
> +
> +			token = strtok_r(tokens, ",", &saved_ptr);
> +
> +			while (token != NULL) {
> +				if (subsys && !strcmp(token, subsys)) {
> +					strcpy(path_v1, mountpoint);
> +					break;
> +				}
> +				token = strtok_r(NULL, ",", &saved_ptr);
> +			}
> +		}
> +
> +		if (!path_v2[0] && !strcmp(type, "cgroup2"))
> +			strcpy(path_v2, mountpoint);
> +
> +		if (path_v1[0] && path_v2[0])
> +			break;
> +	}
> +	fclose(fp);
> +
> +	if (path_v1[0])
> +		path = path_v1;
> +	else if (path_v2[0])
> +		path = path_v2;
> +	else
> +		return -1;
> +
> +	if (strlen(path) < maxlen) {
> +		strcpy(buf, path);
> +		return 0;
> +	}
> +	return -1;
> +}
> diff --git a/tools/lib/api/fs/fs.h b/tools/lib/api/fs/fs.h
> index 92d03b8396b1..07591ecbe39f 100644
> --- a/tools/lib/api/fs/fs.h
> +++ b/tools/lib/api/fs/fs.h
> @@ -28,6 +28,8 @@ FS(bpf_fs)
>  #undef FS
>  
>  
> +int cgroupfs__mountpoint(char *buf, size_t maxlen, const char *subsys);
> +
>  int filename__read_int(const char *filename, int *value);
>  int filename__read_ull(const char *filename, unsigned long long *value);
>  int filename__read_xll(const char *filename, unsigned long long *value);
> diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c
> index 4881d4af3381..12e466d1ec3b 100644
> --- a/tools/perf/util/cgroup.c
> +++ b/tools/perf/util/cgroup.c
> @@ -3,75 +3,16 @@
>  #include "evsel.h"
>  #include "cgroup.h"
>  #include "evlist.h"
> -#include <linux/stringify.h>
>  #include <linux/zalloc.h>
>  #include <sys/types.h>
>  #include <sys/stat.h>
>  #include <fcntl.h>
>  #include <stdlib.h>
>  #include <string.h>
> +#include <api/fs/fs.h>
>  
>  int nr_cgroups;
>  
> -static int
> -cgroupfs_find_mountpoint(char *buf, size_t maxlen)
> -{
> -	FILE *fp;
> -	char mountpoint[PATH_MAX + 1], tokens[PATH_MAX + 1], type[PATH_MAX + 1];
> -	char path_v1[PATH_MAX + 1], path_v2[PATH_MAX + 2], *path;
> -	char *token, *saved_ptr = NULL;
> -
> -	fp = fopen("/proc/mounts", "r");
> -	if (!fp)
> -		return -1;
> -
> -	/*
> -	 * in order to handle split hierarchy, we need to scan /proc/mounts
> -	 * and inspect every cgroupfs mount point to find one that has
> -	 * perf_event subsystem
> -	 */
> -	path_v1[0] = '\0';
> -	path_v2[0] = '\0';
> -
> -	while (fscanf(fp, "%*s %"__stringify(PATH_MAX)"s %"__stringify(PATH_MAX)"s %"
> -				__stringify(PATH_MAX)"s %*d %*d\n",
> -				mountpoint, type, tokens) == 3) {
> -
> -		if (!path_v1[0] && !strcmp(type, "cgroup")) {
> -
> -			token = strtok_r(tokens, ",", &saved_ptr);
> -
> -			while (token != NULL) {
> -				if (!strcmp(token, "perf_event")) {
> -					strcpy(path_v1, mountpoint);
> -					break;
> -				}
> -				token = strtok_r(NULL, ",", &saved_ptr);
> -			}
> -		}
> -
> -		if (!path_v2[0] && !strcmp(type, "cgroup2"))
> -			strcpy(path_v2, mountpoint);
> -
> -		if (path_v1[0] && path_v2[0])
> -			break;
> -	}
> -	fclose(fp);
> -
> -	if (path_v1[0])
> -		path = path_v1;
> -	else if (path_v2[0])
> -		path = path_v2;
> -	else
> -		return -1;
> -
> -	if (strlen(path) < maxlen) {
> -		strcpy(buf, path);
> -		return 0;
> -	}
> -	return -1;
> -}
> -
>  static int open_cgroup(const char *name)
>  {
>  	char path[PATH_MAX + 1];
> @@ -79,7 +20,7 @@ static int open_cgroup(const char *name)
>  	int fd;
>  
>  
> -	if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1))
> +	if (cgroupfs__mountpoint(mnt, PATH_MAX + 1, "perf_event"))
>  		return -1;
>  
>  	scnprintf(path, PATH_MAX, "%s/%s", mnt, name);
> -- 
> 2.25.0.341.g760bfbb309-goog
>