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Subject[PATCH 4/5] cgroup, memcg: move cgroup->event_list[_lock] and event callbacks into memcg
Date
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.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
---
include/linux/cgroup.h | 24 ---------------
include/linux/vmpressure.h | 1 +
kernel/cgroup.c | 2 --
mm/memcontrol.c | 75 ++++++++++++++++++++++++++++++++--------------
4 files changed, 54 insertions(+), 48 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 2ac1021..e33eb7b 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);
@@ -233,10 +232,6 @@ struct cgroup {
struct work_struct destroy_work;
atomic_t css_kill_cnt;

- /* List of events which userspace want to receive */
- struct list_head event_list;
- spinlock_t event_list_lock;
-
/* directory xattrs */
struct simple_xattrs xattrs;
};
@@ -500,25 +495,6 @@ 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 b239482..324ea7a 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;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a0b5e22..2bc45d3 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1352,8 +1352,6 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
cgrp->dummy_css.cgroup = cgrp;
- INIT_LIST_HEAD(&cgrp->event_list);
- spin_lock_init(&cgrp->event_list_lock);
simple_xattrs_init(&cgrp->xattrs);
}

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3700b65..e988bf1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -260,6 +260,22 @@ struct cgroup_event {
*/
struct list_head list;
/*
+ * register_event() callback will be used to add new userspace
+ * waiter for changes related to this event. 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 set,
+ * if you want provide notification functionality.
+ */
+ void (*unregister_event)(struct cgroup_subsys_state *css,
+ struct cftype *cft,
+ struct eventfd_ctx *eventfd);
+ /*
* All fields below needed to unregister event when
* userspace closes eventfd.
*/
@@ -372,6 +388,10 @@ struct mem_cgroup {
atomic_t numainfo_updating;
#endif

+ /* List of events which userspace want to receive */
+ struct list_head event_list;
+ spinlock_t event_list_lock;
+
struct mem_cgroup_per_node *nodeinfo[0];
/* WARNING: nodeinfo must be the last member here */
};
@@ -5970,7 +5990,7 @@ static void cgroup_event_remove(struct work_struct *work)

remove_wait_queue(event->wqh, &event->wait);

- event->cft->unregister_event(css, event->cft, event->eventfd);
+ event->unregister_event(css, event->cft, event->eventfd);

/* Notify userspace the event is going away. */
eventfd_signal(event->eventfd, 1);
@@ -5990,7 +6010,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
{
struct cgroup_event *event = container_of(wait,
struct cgroup_event, wait);
- struct cgroup *cgrp = event->css->cgroup;
+ struct mem_cgroup *memcg = mem_cgroup_from_css(event->css);
unsigned long flags = (unsigned long)key;

if (flags & POLLHUP) {
@@ -6003,7 +6023,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
* side will require wqh->lock via remove_wait_queue(),
* which we hold.
*/
- spin_lock(&cgrp->event_list_lock);
+ spin_lock(&memcg->event_list_lock);
if (!list_empty(&event->list)) {
list_del_init(&event->list);
/*
@@ -6012,7 +6032,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
*/
schedule_work(&event->remove);
}
- spin_unlock(&cgrp->event_list_lock);
+ spin_unlock(&memcg->event_list_lock);
}

return 0;
@@ -6037,6 +6057,7 @@ static void cgroup_event_ptable_queue_proc(struct file *file,
static int cgroup_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 cgroup *cgrp_cfile;
@@ -6104,13 +6125,30 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
goto out_put_cfile;
}

- if (!event->cft->register_event || !event->cft->unregister_event) {
+ /*
+ * Determine the event callbacks and set them in @event. This used
+ * 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.
+ */
+ if (!strcmp(event->cft->name, "usage_in_bytes")) {
+ event->register_event = mem_cgroup_usage_register_event;
+ event->unregister_event = mem_cgroup_usage_unregister_event;
+ } else if (!strcmp(event->cft->name, "oom_control")) {
+ event->register_event = mem_cgroup_oom_register_event;
+ event->unregister_event = mem_cgroup_oom_unregister_event;
+ } else if (!strcmp(event->cft->name, "pressure_level")) {
+ event->register_event = vmpressure_register_event;
+ event->unregister_event = vmpressure_unregister_event;
+ } else if (!strcmp(event->cft->name, "memsw.usage_in_bytes")) {
+ event->register_event = mem_cgroup_usage_register_event;
+ event->unregister_event = mem_cgroup_usage_unregister_event;
+ } else {
ret = -EINVAL;
goto out_put_cfile;
}

- ret = event->cft->register_event(css, event->cft,
- event->eventfd, buffer);
+ ret = event->register_event(css, event->cft, event->eventfd, buffer);
if (ret)
goto out_put_cfile;

@@ -6123,9 +6161,9 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *css,
*/
dget(cgrp->dentry);

- spin_lock(&cgrp->event_list_lock);
- list_add(&event->list, &cgrp->event_list);
- spin_unlock(&cgrp->event_list_lock);
+ spin_lock(&memcg->event_list_lock);
+ list_add(&event->list, &memcg->event_list);
+ spin_unlock(&memcg->event_list_lock);

fput(cfile);
fput(efile);
@@ -6149,8 +6187,6 @@ static struct cftype mem_cgroup_files[] = {
.name = "usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
.read = mem_cgroup_read,
- .register_event = mem_cgroup_usage_register_event,
- .unregister_event = mem_cgroup_usage_unregister_event,
},
{
.name = "max_usage_in_bytes",
@@ -6210,14 +6246,10 @@ static struct cftype mem_cgroup_files[] = {
.name = "oom_control",
.read_map = mem_cgroup_oom_control_read,
.write_u64 = mem_cgroup_oom_control_write,
- .register_event = mem_cgroup_oom_register_event,
- .unregister_event = mem_cgroup_oom_unregister_event,
.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
},
{
.name = "pressure_level",
- .register_event = vmpressure_register_event,
- .unregister_event = vmpressure_unregister_event,
},
#ifdef CONFIG_NUMA
{
@@ -6265,8 +6297,6 @@ static struct cftype memsw_cgroup_files[] = {
.name = "memsw.usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
.read = mem_cgroup_read,
- .register_event = mem_cgroup_usage_register_event,
- .unregister_event = mem_cgroup_usage_unregister_event,
},
{
.name = "memsw.max_usage_in_bytes",
@@ -6457,6 +6487,8 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
mutex_init(&memcg->thresholds_lock);
spin_lock_init(&memcg->move_lock);
vmpressure_init(&memcg->vmpressure);
+ INIT_LIST_HEAD(&memcg->event_list);
+ spin_lock_init(&memcg->event_list_lock);

return &memcg->css;

@@ -6529,7 +6561,6 @@ 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 *cgrp = css->cgroup;
struct cgroup_event *event, *tmp;

/*
@@ -6537,12 +6568,12 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
* Notify userspace about cgroup removing only after rmdir of cgroup
* directory to avoid race between userspace and kernelspace.
*/
- spin_lock(&cgrp->event_list_lock);
- list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
+ spin_lock(&memcg->event_list_lock);
+ list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
list_del_init(&event->list);
schedule_work(&event->remove);
}
- spin_unlock(&cgrp->event_list_lock);
+ spin_unlock(&memcg->event_list_lock);

kmem_cgroup_css_offline(memcg);

--
1.8.3.1


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