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>

1 files changed, 7 insertions, 0 deletions

diff --git a/tools/lib/api/fs/debugfs.c b/tools/lib/api/fs/debugfs.c
index bf9e21648894..d2b18e887071 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"