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Subject[PATCH 5/5] memcg: rename cgroup_event to mem_cgroup_event
Date
cgroup_event is only available in memcg now.  Let's brand it that way.
While at it, add a comment encouraging deprecation of the feature and
remove the respective section from cgroup documentation.

This patch is cosmetic.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
Documentation/cgroups/cgroups.txt | 19 -------------
mm/memcontrol.c | 57 +++++++++++++++++++++++++--------------
2 files changed, 37 insertions(+), 39 deletions(-)

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 638bf17..ca5aee9 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -472,25 +472,6 @@ you give a subsystem a name.
The name of the subsystem appears as part of the hierarchy description
in /proc/mounts and /proc/<pid>/cgroups.

-2.4 Notification API
---------------------
-
-There is mechanism which allows to get notifications about changing
-status of a cgroup.
-
-To register a new notification handler you need to:
- - create a file descriptor for event notification using eventfd(2);
- - open a control file to be monitored (e.g. memory.usage_in_bytes);
- - write "<event_fd> <control_fd> <args>" to cgroup.event_control.
- Interpretation of args is defined by control file implementation;
-
-eventfd will be woken up by control file implementation or when the
-cgroup is removed.
-
-To unregister a notification handler just close eventfd.
-
-NOTE: Support of notifications should be implemented for the control
-file. See documentation for the subsystem.

3. Kernel API
=============
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e988bf1..240ae72 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -242,7 +242,7 @@ struct mem_cgroup_eventfd_list {
/*
* cgroup_event represents events which userspace want to receive.
*/
-struct cgroup_event {
+struct mem_cgroup_event {
/*
* css which the event belongs to.
*/
@@ -5977,14 +5977,27 @@ static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
#endif

/*
+ * DO NOT USE IN NEW FILES.
+ *
+ * "cgroup.event_control" implementation.
+ *
+ * This is way over-engineered. It tries to support fully configureable
+ * events for each user. Such level of flexibility is completely
+ * unnecessary especially in the light of the planned unified hierarchy.
+ *
+ * Please deprecate this and replace with something simpler if at all
+ * possible.
+ */
+
+/*
* Unregister event and free resources.
*
* Gets called from workqueue.
*/
-static void cgroup_event_remove(struct work_struct *work)
+static void memcg_event_remove(struct work_struct *work)
{
- struct cgroup_event *event = container_of(work, struct cgroup_event,
- remove);
+ struct mem_cgroup_event *event = container_of(work,
+ struct mem_cgroup_event, remove);
struct cgroup_subsys_state *css = event->css;
struct cgroup *cgrp = css->cgroup;

@@ -6005,11 +6018,11 @@ static void cgroup_event_remove(struct work_struct *work)
*
* Called with wqh->lock held and interrupts disabled.
*/
-static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
- int sync, void *key)
+static int memcg_event_wake(wait_queue_t *wait, unsigned mode,
+ int sync, void *key)
{
- struct cgroup_event *event = container_of(wait,
- struct cgroup_event, wait);
+ struct mem_cgroup_event *event =
+ container_of(wait, struct mem_cgroup_event, wait);
struct mem_cgroup *memcg = mem_cgroup_from_css(event->css);
unsigned long flags = (unsigned long)key;

@@ -6038,28 +6051,30 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
return 0;
}

-static void cgroup_event_ptable_queue_proc(struct file *file,
+static void memcg_event_ptable_queue_proc(struct file *file,
wait_queue_head_t *wqh, poll_table *pt)
{
- struct cgroup_event *event = container_of(pt,
- struct cgroup_event, pt);
+ struct mem_cgroup_event *event =
+ container_of(pt, struct mem_cgroup_event, pt);

event->wqh = wqh;
add_wait_queue(wqh, &event->wait);
}

/*
+ * DO NOT USE IN NEW FILES.
+ *
* Parse input and register new memcg event handler.
*
* Input must be in format '<event_fd> <control_fd> <args>'.
* Interpretation of args is defined by control file implementation.
*/
-static int cgroup_write_event_control(struct cgroup_subsys_state *css,
- struct cftype *cft, const char *buffer)
+static int memcg_write_event_control(struct cgroup_subsys_state *css,
+ struct cftype *cft, const char *buffer)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
struct cgroup *cgrp = css->cgroup;
- struct cgroup_event *event;
+ struct mem_cgroup_event *event;
struct cgroup *cgrp_cfile;
unsigned int efd, cfd;
struct file *efile;
@@ -6082,9 +6097,9 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
return -ENOMEM;
event->css = css;
INIT_LIST_HEAD(&event->list);
- init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
- init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
- INIT_WORK(&event->remove, cgroup_event_remove);
+ init_poll_funcptr(&event->pt, memcg_event_ptable_queue_proc);
+ init_waitqueue_func_entry(&event->wait, memcg_event_wake);
+ INIT_WORK(&event->remove, memcg_event_remove);

efile = eventfd_fget(efd);
if (IS_ERR(efile)) {
@@ -6130,6 +6145,8 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
* to be done via struct cftype but cgroup core no longer knows
* about these events. The following is crude but the whole thing
* is for compatibility anyway.
+ *
+ * DO NOT ADD NEW FILES.
*/
if (!strcmp(event->cft->name, "usage_in_bytes")) {
event->register_event = mem_cgroup_usage_register_event;
@@ -6227,8 +6244,8 @@ static struct cftype mem_cgroup_files[] = {
.read_u64 = mem_cgroup_hierarchy_read,
},
{
- .name = "cgroup.event_control",
- .write_string = cgroup_write_event_control,
+ .name = "cgroup.event_control", /* XXX: for compat */
+ .write_string = memcg_write_event_control,
.flags = CFTYPE_NO_PREFIX,
.mode = S_IWUGO,
},
@@ -6561,7 +6578,7 @@ static void mem_cgroup_invalidate_reclaim_iterators(struct mem_cgroup *memcg)
static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
- struct cgroup_event *event, *tmp;
+ struct mem_cgroup_event *event, *tmp;

/*
* Unregister events and notify userspace.
--
1.8.3.1


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