Using eventfd user space can generate POLLIN/POLLOUT events but some
applications may want to generate POLLPRI/POLLERR events as well.
This patch submission aims to generalize the events generated by an
eventfd. This is a resubmission of a patch from Feb 2013[1]. The original
discussion trailed off without any conclusion, but the original author
has recently confirmed[2] that this functionality is still useful, so I
volunteered to rebase and resubmit the patch for discussion.

[1] https://lkml.org/lkml/2013/2/18/147
[2] https://lkml.org/lkml/2015/7/9/153

Changes in v3
-------------
* replace efd_mask structure with scalar 'events' variable.

Changes in v2
-------------

* rebased on Linux v4.3-rc1
* Move file operation implementations for EFD_MASK to a seperate structure
* Remove 'data' element from efd_mask structure
* read() is no longer supported when EFD_MASK is set (fails with EINVAL)
* eventfd_ctx_fileget() now returns EINVAL when EFD_MASK is set, eliminating
  the possibility of triggering the orginal BUG_ON() macros which have now
  been removed.

Thank you,
Damian

Martin Sustrik (1):
  eventfd: implementation of EFD_MASK flag

 fs/eventfd.c                 | 91 ++++++++++++++++++++++++++++++++++++++------
 include/linux/eventfd.h      | 16 +-------
 include/uapi/linux/eventfd.h | 40 +++++++++++++++++++
 3 files changed, 121 insertions(+), 26 deletions(-)
 create mode 100644 include/uapi/linux/eventfd.h

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1.9.1