cgroup, memcg: move cgroup->event_list[_lock] and event callbacks into memcg

cgroup_event is being moved from cgroup core to memcg and the
implementation is already moved by the previous patch.  This patch
moves the data fields and callbacks.

* cgroup->event_list[_lock] are moved to mem_cgroup.

* cftype->[un]register_event() are moved to cgroup_event.  This makes
  it impossible for individual cftype definitions to specify their
  event callbacks.  This is worked around by simply hard-coding
  filename to event callback mapping in cgroup_write_event_control().
  This is awkward and inflexible, which is actually desirable given
  that we don't want to grow more usages of this feature.

* eventfd_ctx declaration is removed from cgroup.h, which makes
  vmpressure.h miss eventfd_ctx declaration.  Include eventfd.h from
  vmpressure.h.

v2: Use file name from dentry instead of cftype.  This will allow
    removing all cftype handling in the function.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>

2 files changed, 1 insertions, 24 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 40c2427806c9..612adc5b87c5 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -29,7 +29,6 @@ struct cgroup_subsys;
 struct inode;
 struct cgroup;
 struct css_id;
-struct eventfd_ctx;
 
 extern int cgroup_init_early(void);
 extern int cgroup_init(void);
@@ -239,10 +238,6 @@ struct cgroup {
         struct rcu_head rcu_head;
         struct work_struct destroy_work;
 
-        /* List of events which userspace want to receive */
-        struct list_head event_list;
-        spinlock_t event_list_lock;
-
         /* directory xattrs */
         struct simple_xattrs xattrs;
 };
@@ -506,25 +501,6 @@ struct cftype {
         int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
 
         int (*release)(struct inode *inode, struct file *file);
-
-        /*
-         * register_event() callback will be used to add new userspace
-         * waiter for changes related to the cftype. Implement it if
-         * you want to provide this functionality. Use eventfd_signal()
-         * on eventfd to send notification to userspace.
-         */
-        int (*register_event)(struct cgroup_subsys_state *css,
-                              struct cftype *cft, struct eventfd_ctx *eventfd,
-                              const char *args);
-        /*
-         * unregister_event() callback will be called when userspace
-         * closes the eventfd or on cgroup removing.
-         * This callback must be implemented, if you want provide
-         * notification functionality.
-         */
-        void (*unregister_event)(struct cgroup_subsys_state *css,
-                                 struct cftype *cft,
-                                 struct eventfd_ctx *eventfd);
 };
 
 /*
diff --git a/include/linux/vmpressure.h b/include/linux/vmpressure.h
index 3f3788d49362..9dd1914f1a6c 100644
--- a/include/linux/vmpressure.h
+++ b/include/linux/vmpressure.h
@@ -7,6 +7,7 @@
 #include <linux/gfp.h>
 #include <linux/types.h>
 #include <linux/cgroup.h>
+#include <linux/eventfd.h>
 
 struct vmpressure {
         unsigned long scanned;