2 files changed, 111 insertions, 9 deletions

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 6cab1f29da4c..eac22d3b2f7b 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -184,6 +184,9 @@ limits on the root cgroup.
 
 Note2: When panic_on_oom is set to "2", the whole system will panic.
 
+When oom event notifier is registered, event will be delivered.
+(See oom_control section)
+
 2. Locking
 
 The memory controller uses the following hierarchy
@@ -488,7 +491,22 @@ threshold in any direction.
 
 It's applicable for root and non-root cgroup.
 
-10. TODO
+10. OOM Control
+
+Memory controler implements oom notifier using cgroup notification
+API (See cgroups.txt). It allows to register multiple oom notification
+delivery and gets notification when oom happens.
+
+To register a notifier, application need:
+ - create an eventfd using eventfd(2)
+ - open memory.oom_control file
+ - write string like "<event_fd> <memory.oom_control>" to cgroup.event_control
+
+Application will be notifier through eventfd when oom happens.
+OOM notification doesn't work for root cgroup.
+
+
+11. TODO
 
 1. Add support for accounting huge pages (as a separate controller)
 2. Make per-cgroup scanner reclaim not-shared pages first
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 94ac208b1490..da2ed3913316 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -149,6 +149,7 @@ struct mem_cgroup_threshold {
         u64 threshold;
 };
 
+/* For threshold */
 struct mem_cgroup_threshold_ary {
         /* An array index points to threshold just below usage. */
         atomic_t current_threshold;
@@ -157,8 +158,14 @@ struct mem_cgroup_threshold_ary {
         /* Array of thresholds */
         struct mem_cgroup_threshold entries[0];
 };
+/* for OOM */
+struct mem_cgroup_eventfd_list {
+        struct list_head list;
+        struct eventfd_ctx *eventfd;
+};
 
 static void mem_cgroup_threshold(struct mem_cgroup *mem);
+static void mem_cgroup_oom_notify(struct mem_cgroup *mem);
 
 /*
  * The memory controller data structure. The memory controller controls both
@@ -220,6 +227,9 @@ struct mem_cgroup {
         /* thresholds for mem+swap usage. RCU-protected */
         struct mem_cgroup_threshold_ary *memsw_thresholds;
 
+        /* For oom notifier event fd */
+        struct list_head oom_notify;
+
         /*
          * Should we move charges of a task when a task is moved into this
          * mem_cgroup ? And what type of charges should we move ?
@@ -282,9 +292,12 @@ enum charge_type {
 /* for encoding cft->private value on file */
 #define _MEM                    (0)
 #define _MEMSWAP                (1)
+#define _OOM_TYPE               (2)
 #define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
 #define MEMFILE_TYPE(val)       (((val) >> 16) & 0xffff)
 #define MEMFILE_ATTR(val)       ((val) & 0xffff)
+/* Used for OOM nofiier */
+#define OOM_CONTROL             (0)
 
 /*
  * Reclaim flags for mem_cgroup_hierarchical_reclaim
@@ -1353,6 +1366,8 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
          */
         if (!locked)
                 prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
+        else
+                mem_cgroup_oom_notify(mem);
         mutex_unlock(&memcg_oom_mutex);
 
         if (locked)
@@ -3398,8 +3413,22 @@ static int compare_thresholds(const void *a, const void *b)
         return _a->threshold - _b->threshold;
 }
 
-static int mem_cgroup_register_event(struct cgroup *cgrp, struct cftype *cft,
-                struct eventfd_ctx *eventfd, const char *args)
+static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem, void *data)
+{
+        struct mem_cgroup_eventfd_list *ev;
+
+        list_for_each_entry(ev, &mem->oom_notify, list)
+                eventfd_signal(ev->eventfd, 1);
+        return 0;
+}
+
+static void mem_cgroup_oom_notify(struct mem_cgroup *mem)
+{
+        mem_cgroup_walk_tree(mem, NULL, mem_cgroup_oom_notify_cb);
+}
+
+static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
+        struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
         struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
@@ -3483,8 +3512,8 @@ unlock:
         return ret;
 }
 
-static int mem_cgroup_unregister_event(struct cgroup *cgrp, struct cftype *cft,
-                struct eventfd_ctx *eventfd)
+static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
+        struct cftype *cft, struct eventfd_ctx *eventfd)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
         struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
@@ -3568,13 +3597,61 @@ unlock:
         return ret;
 }
 
+static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
+        struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
+{
+        struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+        struct mem_cgroup_eventfd_list *event;
+        int type = MEMFILE_TYPE(cft->private);
+
+        BUG_ON(type != _OOM_TYPE);
+        event = kmalloc(sizeof(*event), GFP_KERNEL);
+        if (!event)
+                return -ENOMEM;
+
+        mutex_lock(&memcg_oom_mutex);
+
+        event->eventfd = eventfd;
+        list_add(&event->list, &memcg->oom_notify);
+
+        /* already in OOM ? */
+        if (atomic_read(&memcg->oom_lock))
+                eventfd_signal(eventfd, 1);
+        mutex_unlock(&memcg_oom_mutex);
+
+        return 0;
+}
+
+static int mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
+        struct cftype *cft, struct eventfd_ctx *eventfd)
+{
+        struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+        struct mem_cgroup_eventfd_list *ev, *tmp;
+        int type = MEMFILE_TYPE(cft->private);
+
+        BUG_ON(type != _OOM_TYPE);
+
+        mutex_lock(&memcg_oom_mutex);
+
+        list_for_each_entry_safe(ev, tmp, &mem->oom_notify, list) {
+                if (ev->eventfd == eventfd) {
+                        list_del(&ev->list);
+                        kfree(ev);
+                }
+        }
+
+        mutex_unlock(&memcg_oom_mutex);
+
+        return 0;
+}
+
 static struct cftype mem_cgroup_files[] = {
         {
                 .name = "usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
                 .read_u64 = mem_cgroup_read,
-                .register_event = mem_cgroup_register_event,
-                .unregister_event = mem_cgroup_unregister_event,
+                .register_event = mem_cgroup_usage_register_event,
+                .unregister_event = mem_cgroup_usage_unregister_event,
         },
         {
                 .name = "max_usage_in_bytes",
@@ -3623,6 +3700,12 @@ static struct cftype mem_cgroup_files[] = {
                 .read_u64 = mem_cgroup_move_charge_read,
                 .write_u64 = mem_cgroup_move_charge_write,
         },
+        {
+                .name = "oom_control",
+                .register_event = mem_cgroup_oom_register_event,
+                .unregister_event = mem_cgroup_oom_unregister_event,
+                .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
+        },
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
@@ -3631,8 +3714,8 @@ static struct cftype memsw_cgroup_files[] = {
                 .name = "memsw.usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
                 .read_u64 = mem_cgroup_read,
-                .register_event = mem_cgroup_register_event,
-                .unregister_event = mem_cgroup_unregister_event,
+                .register_event = mem_cgroup_usage_register_event,
+                .unregister_event = mem_cgroup_usage_unregister_event,
         },
         {
                 .name = "memsw.max_usage_in_bytes",
@@ -3878,6 +3961,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
         }
         mem->last_scanned_child = 0;
         spin_lock_init(&mem->reclaim_param_lock);
+        INIT_LIST_HEAD(&mem->oom_notify);
 
         if (parent)
                 mem->swappiness = get_swappiness(parent);