Add pidfd support to the fanotify API

Hey Jan/Amir/Christian,

This is the updated patch series for adding pidfd support to the
fanotify API. It incorporates all the suggestions that had come out of
the initial RFC patch series [0].

The main difference with this patch series is that FAN_REPORT_PIDFD
results in an additional info record object supplied alongside the
generic event metadata object instead of overloading metadata->pid. If
any of the fid flavoured init flags are specified, then the pidfd info
record object will follow any fid info record objects.

[0] https://www.spinics.net/lists/linux-fsdevel/msg193296.html

Matthew Bobrowski (5):
  kernel/pid.c: remove static qualifier from pidfd_create()
  kernel/pid.c: implement checks on parameters passed to pidfd_create()
  fanotify_user.c: minor cosmetic adjustments to fid labels
  fanotify/fanotify_user.c: introduce a generic info record copying
    function
  fanotify: Add pidfd info record support to the fanotify API

 fs/notify/fanotify/fanotify_user.c | 216 +++++++++++++++++++----------
 include/linux/fanotify.h           |   3 +
 include/linux/pid.h                |   1 +
 include/uapi/linux/fanotify.h      |  12 ++
 kernel/pid.c                       |  15 +-
 5 files changed, 170 insertions(+), 77 deletions(-)

-- 
2.31.1.751.gd2f1c929bd-goog

/M