CGroup API files: add cgroup map data type
Adds a new type of supported control file representation, a map from strings
to u64 values.
Each map entry is printed as a line in a similar format to /proc/vmstat, i.e.
"$key $value\n"
Signed-off-by: Paul Menage <menage@google.com>
Cc: "Li Zefan" <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "YAMAMOTO Takashi" <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 058371c..0a3ab67 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -166,6 +166,16 @@
};
+/*
+ * cgroup_map_cb is an abstract callback API for reporting map-valued
+ * control files
+ */
+
+struct cgroup_map_cb {
+ int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
+ void *state;
+};
+
/* struct cftype:
*
* The files in the cgroup filesystem mostly have a very simple read/write
@@ -194,6 +204,15 @@
* single integer. Use it in place of read()
*/
u64 (*read_u64) (struct cgroup *cgrp, struct cftype *cft);
+ /*
+ * read_map() is used for defining a map of key/value
+ * pairs. It should call cb->fill(cb, key, value) for each
+ * entry. The key/value pairs (and their ordering) should not
+ * change between reboots.
+ */
+ int (*read_map) (struct cgroup *cont, struct cftype *cft,
+ struct cgroup_map_cb *cb);
+
ssize_t (*write) (struct cgroup *cgrp, struct cftype *cft,
struct file *file,
const char __user *buf, size_t nbytes, loff_t *ppos);