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    Subjectfanotify issues in 2.6.34-rc6-next-20100506
    I have started to have a look at the fanotify system, based on information
    gleaned from:

    [1] http://people.redhat.com/~eparis/fanotify/
    [2] http://lwn.net/Articles/360955/

    Unfortunately there seems to be some bug in the current implemenation, since
    running a patched version of the fanotify.c application found in [1]

    --- fanotify.c.orig 2010-03-27 05:26:27.000000000 +0100
    +++ fanotify.c 2010-05-07 10:56:38.000000000 +0200
    @@ -125,7 +125,7 @@
    fan_mask |= FAN_ALL_PERM_EVENTS;

    // fanotify_init(flags, event_f_flags, priority)
    - fan_fd = fanotify_init(0, O_RDONLY | O_LARGEFILE, 0);
    + fan_fd = fanotify_init(0, 0, 0);
    if (fan_fd < 0)
    goto fail;

    seems to lose/corrupt events. For instance running 'fanotify -c /dir/to/watch'
    and then running the command 'cd /dir/to/watch ; touch a b c d e f g h i j k l'
    might generate (results are more or less random):
    /dir/to/watch/a: pid=18584 open
    /dir/to/watch/a: pid=18584 close(writable)
    /dir/to/watch/b: pid=18584 open # 2 open events for b
    /dir/to/watch/b: pid=18584 open close(writable) #
    /dir/to/watch/d: pid=18584 open # events for c missing
    /dir/to/watch/d: pid=18584 open close(writable) # 2 open events for d
    /dir/to/watch/f: pid=18584 open close(writable) # events for e missing
    /dir/to/watch/g: pid=18584 open close(writable)
    /dir/to/watch/h: pid=18584 open close(writable)
    /dir/to/watch/i: pid=18584 open close(writable)
    /dir/to/watch/j: pid=18584 open
    /dir/to/watch/j: pid=18584 close(writable)
    /dir/to/watch/k: pid=18584 open
    /dir/to/watch/k: pid=18584 open close(writable) # 2 open events for k
    /dir/to/watch/l: pid=18584 close(writable) # no open event for l

    A similar program using inotify gets all events correctly.


    I have also problems with the fact that the following sequence dosn't leave a
    trace in the fanotify events:

    mkdir /dir/not/watched
    touch /dir/not/watched/z
    ln /dir/not/watched/z /dir/to/watch/z
    rm /dir/not/watched/z
    rmdir /dir/not/watched)

    What is the rationale for not reporting link/unlink events via fanotify?

    Best regards

    Anders Blomdell

    --
    Anders Blomdell Email: anders.blomdell@control.lth.se
    Department of Automatic Control
    Lund University Phone: +46 46 222 4625
    P.O. Box 118 Fax: +46 46 138118
    SE-221 00 Lund, Sweden


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