linux-kernel - Re: [PATCH 11/15] tools lib api: Add mount support for fs

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Message-ID: <20150904142631.GB658@krava.redhat.com>
Date:	Fri, 4 Sep 2015 16:26:31 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Raphaël Beamonte <raphael.beamonte@...il.com>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 11/15] tools lib api: Add mount support for fs

On Fri, Sep 04, 2015 at 10:14:28AM -0400, Raphaël Beamonte wrote:
> 2015-09-02 3:56 GMT-04:00 Jiri Olsa <jolsa@...nel.org>:
> > Adding name__mount (where name is in sysfs,procfs,debugfs,tracefs)
> > interface that tries to mount the filesystem in case no mount is found.
> >
> > Link: http://lkml.kernel.org/n/tip-ja49vwfiq2qqkmoxx9yk26lm@git.kernel.org
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> >  tools/lib/api/fs/fs.c | 44 +++++++++++++++++++++++++++++++++++++++-----
> >  tools/lib/api/fs/fs.h | 15 +++++++++++----
> >  2 files changed, 50 insertions(+), 9 deletions(-)
> 
> Why automatic mounting the **fs filesystems?
> Isn't it better to let the user decide when and where to mount it if
> s/he forgot to do it before? Forcing a mount is also potentially
> forcing to umount then mount when mounting has been forgotten before.

well, I guess at some point we decided this was a good idea
to make perf more user friendly

AFAICS we do this only for debugfs and tracefs.. procfs
and sysfs are mounted most of the time anyway 

we could track and unmount on exit, but I'd say let's have
someone complaining about it first ;-)

jirka

> 
> 
> > diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
> > index ef16d2a83a27..bc93baf33fff 100644
> > --- a/tools/lib/api/fs/fs.c
> > +++ b/tools/lib/api/fs/fs.c
> > @@ -9,6 +9,7 @@
> >  #include <sys/stat.h>
> >  #include <fcntl.h>
> >  #include <unistd.h>
> > +#include <sys/mount.h>
> >
> >  #include "debugfs.h"
> >  #include "fs.h"
> > @@ -215,16 +216,49 @@ static const char *fs__mountpoint(int idx)
> >         return fs__get_mountpoint(fs);
> >  }
> >
> > -#define FS__MOUNTPOINT(name, idx)      \
> > +static const char *mount_overload(struct fs *fs)
> > +{
> > +       size_t name_len = strlen(fs->name);
> > +       /* "PERF_" + name + "_ENVIRONMENT" + '\0' */
> > +       char upper_name[5 + name_len + 12 + 1];
> > +
> > +       snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
> > +       mem_toupper(upper_name, name_len);
> > +
> > +       return getenv(upper_name) ?: *fs->mounts;
> > +}
> > +
> > +static const char *fs__mount(int idx)
> > +{
> > +       struct fs *fs = &fs__entries[idx];
> > +       const char *mountpoint;
> > +
> > +       if (fs__mountpoint(idx))
> > +               return (const char *)fs->path;
> > +
> > +       mountpoint = mount_overload(fs);
> > +
> > +       if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
> > +               return NULL;
> > +
> > +       return fs__check_mounts(fs) ? fs->path : NULL;
> > +}
> > +
> > +#define FS(name, idx)                  \
> >  const char *name##__mountpoint(void)   \
> >  {                                      \
> >         return fs__mountpoint(idx);     \
> > +}                                      \
> > +                                       \
> > +const char *name##__mount(void)                \
> > +{                                      \
> > +       return fs__mount(idx);          \
> >  }
> >
> > -FS__MOUNTPOINT(sysfs,   FS__SYSFS);
> > -FS__MOUNTPOINT(procfs,  FS__PROCFS);
> > -FS__MOUNTPOINT(debugfs, FS__DEBUGFS);
> > -FS__MOUNTPOINT(tracefs, FS__TRACEFS);
> > +FS(sysfs,   FS__SYSFS);
> > +FS(procfs,  FS__PROCFS);
> > +FS(debugfs, FS__DEBUGFS);
> > +FS(tracefs, FS__TRACEFS);
> >
> >  int filename__read_int(const char *filename, int *value)
> >  {
> > diff --git a/tools/lib/api/fs/fs.h b/tools/lib/api/fs/fs.h
> > index 9013227ae0d1..a9627ea5e6ae 100644
> > --- a/tools/lib/api/fs/fs.h
> > +++ b/tools/lib/api/fs/fs.h
> > @@ -9,10 +9,17 @@
> >  #define PATH_MAX 4096
> >  #endif
> >
> > -const char *sysfs__mountpoint(void);
> > -const char *procfs__mountpoint(void);
> > -const char *debugfs__mountpoint(void);
> > -const char *tracefs__mountpoint(void);
> > +#define FS(name)                               \
> > +       const char *name##__mountpoint(void);   \
> > +       const char *name##__mount(void);
> > +
> > +FS(sysfs)
> > +FS(procfs)
> > +FS(debugfs)
> > +FS(tracefs)
> > +
> > +#undef FS
> > +
> >
> >  int filename__read_int(const char *filename, int *value);
> >  int sysctl__read_int(const char *sysctl, int *value);
> > --
> > 2.4.3
> >
--
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