[patch 4/4] timerfd.2: Add ioctl method description

ioctl(2)
	The following commands are supported: TFD_IOC_SET_TICKS to adjust
	the number of the timer expirations that have occurred.
	It take a pointer to nonzero 8-byte integer (uint64_t*) containing
	new number of expirations. Once the number is set any waiter on
	the timer is woken up. The only purpose of this command is to restore
	the expirations in a sake of checkpoint/restore procedure.
	It requires the kernel to be built with CONFIG_CHECKPOINT_RESTORE
	support.

Signed-off-by: Cyrill Gorcunov <redacted>
CC: Michael Kerrisk <redacted>
CC: Thomas Gleixner <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andrey Vagin <redacted>
CC: Pavel Emelyanov <redacted>
CC: Vladimir Davydov <redacted>
CC: linux-api@vger.kernel.org
---
 man2/timerfd_create.2 |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

Index: man-pages/man2/timerfd_create.2
===================================================================

--- man-pages.orig/man2/timerfd_create.2
+++ man-pages/man2/timerfd_create.2

@@ -260,6 +260,20 @@ multiplexing APIs:
 and
 .BR epoll (7).
 .TP
+.BR ioctl "(2)"
+The following commands are supported:
+.B TFD_IOC_SET_TICKS
+to adjust the number of the timer expirations that have occurred.
+It take a pointer to nonzero 8-byte integer
+.RI ( uint64_t *)
+containing the new number of expirations.
+Once the number is set any waiter on the timer is woken up.
+The only purpose of this command is to restore the expirations
+in a sake of checkpoint/restore procedure.
+It requires the kernel to be built with
+.BR CONFIG_CHECKPOINT_RESTORE
+support.
+.TP
 .BR close (2)
 When the file descriptor is no longer required it should be closed.
 When all file descriptors associated with the same timer object