linux-kernel - Re: [PATCH] tools lib api fs: Store tracing mountpoint for better error message

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Date:	Sat, 19 Sep 2015 17:00:58 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Raphaël Beamonte <raphael.beamonte@...il.com>
Subject: Re: [PATCH] tools lib api fs: Store tracing mountpoint for better
 error message

On Sat, Sep 19, 2015 at 08:50:19AM -0600, David Ahern wrote:
> On 9/19/15 8:47 AM, Jiri Olsa wrote:
> 
> >diff --git a/tools/lib/api/fs/tracing_path.c b/tools/lib/api/fs/tracing_path.c
> >index 38aca2dd1946..0406a7d5c891 100644
> >--- a/tools/lib/api/fs/tracing_path.c
> >+++ b/tools/lib/api/fs/tracing_path.c
> >@@ -12,12 +12,14 @@
> >  #include "tracing_path.h"
> >
> >
> >+char tracing_mnt[PATH_MAX + 1]         = "/sys/kernel/debug";
> >  char tracing_path[PATH_MAX + 1]        = "/sys/kernel/debug/tracing";
> >  char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
> 
> why all the +1s? null terminator has to fit within PATH_MAX as well.

good question.. can't see a reason ATM

jirka

> 
> >
> >
> >  static void __tracing_path_set(const char *tracing, const char *mountpoint)
> >  {
> >+	snprintf(tracing_mnt, sizeof(tracing_mnt), "%s", mountpoint);
> >  	snprintf(tracing_path, sizeof(tracing_path), "%s/%s",
> >  		 mountpoint, tracing);
> >  	snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s%s",
> >@@ -109,19 +111,10 @@ static int strerror_open(int err, char *buf, size_t size, const char *filename)
> >  			 "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
> >  		break;
> >  	case EACCES: {
> >-		const char *mountpoint = debugfs__mountpoint();
> >-
> >-		if (!access(mountpoint, R_OK) && strncmp(filename, "tracing/", 8) == 0) {
> >-			const char *tracefs_mntpoint = tracefs__mountpoint();
> >-
> >-			if (tracefs_mntpoint)
> >-				mountpoint = tracefs__mountpoint();
> >-		}
> >-
> >  		snprintf(buf, size,
> >  			 "Error:\tNo permissions to read %s/%s\n"
> >  			 "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
> >-			 tracing_events_path, filename, mountpoint);
> >+			 tracing_events_path, filename, tracing_mnt);
> >  	}
> >  		break;
> >  	default:
> >
> 
> LGTM.
> 
> David
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