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Subject[PATCH 1/3] 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>

---
include/linux/cgroup.h | 8 ++++++++
kernel/cgroup.c | 4 ++++
2 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 785a01c..2d1d151 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);
};

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e8e8ec4..f2d8f25 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1410,6 +1410,10 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
return cft->write(cgrp, cft, file, buf, nbytes, ppos);
if (cft->write_u64 || cft->write_s64)
return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
+ if (cft->trigger) {
+ int ret = cft->trigger(cgrp, (unsigned int)cft->private);
+ return ret ? ret : nbytes;
+ }
return -EINVAL;
}

--
1.5.3.4



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