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    Subject[PATCH 04/39] tools lib api fs: Store tracing mountpoint for better error message
    Date
    From: Jiri Olsa <jolsa@kernel.org>

    Storing the actual tracing path mountpoint to display correct
    error message hint ('Hint:' line). The error hint rediscovers
    mountpoints, but it could be different from what we actually
    used in tracing path.

    Before we'd display debugfs mount even though tracefs was used:
    $ perf record -e sched:sched_krava ls
    event syntax error: 'sched:sched_krava'
    \___ can't access trace events

    Error: No permissions to read /sys/kernel/debug/tracing/events/sched/sched_krava
    Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug'
    ...

    After this change, correct mountpoint is displayed:
    $ perf record -e sched:sched_krava ls
    event syntax error: 'sched:sched_krava'
    \___ can't access trace events

    Error: No permissions to read /sys/kernel/debug/tracing/events/sched/sched_krava
    Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing'
    ...

    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Matt Fleming <matt@codeblueprint.co.uk>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Raphael Beamonte <raphael.beamonte@gmail.com>
    Link: http://lkml.kernel.org/r/1442674027-19427-1-git-send-email-jolsa@kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    ---
    tools/lib/api/fs/tracing_path.c | 13 +++----------
    1 file changed, 3 insertions(+), 10 deletions(-)

    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";


    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:
    --
    2.1.0


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