[tip:perf/core] tools lib fs debugfs: Check if debugfs is mounted when handling ENOENT

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  f816b3cc99804a9f771315331deb36abec47f5b4
Gitweb:     http://git.kernel.org/tip/f816b3cc99804a9f771315331deb36abec47f5b4
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Thu, 22 Jan 2015 16:35:42 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 22 Jan 2015 17:02:23 -0300

tools lib fs debugfs: Check if debugfs is mounted when handling ENOENT

If debugfs was already mounted, then its a matter of not finding the
tracepoint, tell the user that perhaps a CONFIG_ setting is not enabled.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-6chfytoflyx3jwfqm7ebltu0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/api/fs/debugfs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/lib/api/fs/debugfs.c b/tools/lib/api/fs/debugfs.c
index bf9e216..d2b18e8 100644
--- a/tools/lib/api/fs/debugfs.c
+++ b/tools/lib/api/fs/debugfs.c
@@ -106,6 +106,13 @@ int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename
 
 	switch (err) {
 	case ENOENT:
+		if (debugfs_found) {
+			snprintf(buf, size,
+				 "Error:\tFile %s/%s not found.\n"
+				 "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
+				 debugfs_mountpoint, filename);
+			break;
+		}
 		snprintf(buf, size, "%s",
 			 "Error:\tUnable to find debugfs\n"
 			 "Hint:\tWas your kernel compiled with debugfs support?\n"