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

[Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>]

Em Tue, Jan 28, 2020 at 10:40:57AM +0100, Jiri Olsa escreveu:
> 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@redhat.com>
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> 
> Acked-by: Jiri Olsa <jolsa@redhat.com>

Thanks, applied to perf/core.

- Arnaldo
 
> 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
> > 
> 

-- 

- Arnaldo