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Date: Tue, 28 Jan 2020 10:40:57 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2] tools lib api fs: Move cgroupsfs__mountpoint()
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@...hat.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Acked-by: Jiri Olsa <jolsa@...hat.com>
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
>
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