cgroups: add the trigger callback to struct cftype

Trigger callback can be used to receive a kick-up from the user space.  The
string written is ignored.

The cftype->private is used for multiplexing events.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Paul Menage <menage@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 785a01cfb49d..2d1d151258cf 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -243,6 +243,14 @@ struct cftype {
          */
         int (*write_s64) (struct cgroup *cgrp, struct cftype *cft, s64 val);
 
+        /*
+         * trigger() callback can be used to get some kick from the
+         * userspace, when the actual string written is not important
+         * at all. The private field can be used to determine the
+         * kick type for multiplexing.
+         */
+        int (*trigger)(struct cgroup *cgrp, unsigned int event);
+
         int (*release) (struct inode *inode, struct file *file);
 };