memory controller: soft limit interface

Add an interface to allow get/set of soft limits.  Soft limits for memory
plus swap controller (memsw) is currently not supported.  Resource
counters have been enhanced to support soft limits and new type
RES_SOFT_LIMIT has been added.  Unlike hard limits, soft limits can be
directly set and do not need any reclaim or checks before setting them to
a newer value.

Kamezawa-San raised a question as to whether soft limit should belong to
res_counter.  Since all resources understand the basic concepts of hard
and soft limits, it is justified to add soft limits here.  Soft limits are
a generic resource usage feature, even file system quotas support soft
limits.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 58 insertions, 0 deletions

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index 511f42fc6816..fcb9884df618 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -35,6 +35,10 @@ struct res_counter {
          */
         unsigned long long limit;
         /*
+         * the limit that usage can be exceed
+         */
+        unsigned long long soft_limit;
+        /*
          * the number of unsuccessful attempts to consume the resource
          */
         unsigned long long failcnt;
@@ -87,6 +91,7 @@ enum {
         RES_MAX_USAGE,
         RES_LIMIT,
         RES_FAILCNT,
+        RES_SOFT_LIMIT,
 };
 
 /*
@@ -132,6 +137,36 @@ static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
         return false;
 }
 
+static inline bool res_counter_soft_limit_check_locked(struct res_counter *cnt)
+{
+        if (cnt->usage < cnt->soft_limit)
+                return true;
+
+        return false;
+}
+
+/**
+ * Get the difference between the usage and the soft limit
+ * @cnt: The counter
+ *
+ * Returns 0 if usage is less than or equal to soft limit
+ * The difference between usage and soft limit, otherwise.
+ */
+static inline unsigned long long
+res_counter_soft_limit_excess(struct res_counter *cnt)
+{
+        unsigned long long excess;
+        unsigned long flags;
+
+        spin_lock_irqsave(&cnt->lock, flags);
+        if (cnt->usage <= cnt->soft_limit)
+                excess = 0;
+        else
+                excess = cnt->usage - cnt->soft_limit;
+        spin_unlock_irqrestore(&cnt->lock, flags);
+        return excess;
+}
+
 /*
  * Helper function to detect if the cgroup is within it's limit or
  * not. It's currently called from cgroup_rss_prepare()
@@ -147,6 +182,17 @@ static inline bool res_counter_check_under_limit(struct res_counter *cnt)
         return ret;
 }
 
+static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
+{
+        bool ret;
+        unsigned long flags;
+
+        spin_lock_irqsave(&cnt->lock, flags);
+        ret = res_counter_soft_limit_check_locked(cnt);
+        spin_unlock_irqrestore(&cnt->lock, flags);
+        return ret;
+}
+
 static inline void res_counter_reset_max(struct res_counter *cnt)
 {
         unsigned long flags;
@@ -180,4 +226,16 @@ static inline int res_counter_set_limit(struct res_counter *cnt,
         return ret;
 }
 
+static inline int
+res_counter_set_soft_limit(struct res_counter *cnt,
+                                unsigned long long soft_limit)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&cnt->lock, flags);
+        cnt->soft_limit = soft_limit;
+        spin_unlock_irqrestore(&cnt->lock, flags);
+        return 0;
+}
+
 #endif