Add an interface to set limit. This is necessary to memory resource controller

because it shrinks usage at set limit.
(*) Other controller may not need this interface to shrink usage because

    shrinking is not necessary or impossible in it.
Changelog:

  - fixed white space bug.
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
 include/linux/res_counter.h |   15 +++++++++++++++

 1 file changed, 15 insertions(+)
Index: test-2.6.26-rc8-mm1/include/linux/res_counter.h

===================================================================

--- test-2.6.26-rc8-mm1.orig/include/linux/res_counter.h

+++ test-2.6.26-rc8-mm1/include/linux/res_counter.h

@@ -176,4 +176,19 @@ static inline bool res_counter_can_add(s

 	return ret;

 }
+static inline int res_counter_set_limit(struct res_counter *cnt,

+	unsigned long long limit)

+{

+	unsigned long flags;

+	int ret = -EBUSY;

+

+	spin_lock_irqsave(&cnt->lock, flags);

+	if (cnt->usage < limit) {

+		cnt->limit = limit;

+		ret = 0;

+	}

+	spin_unlock_irqrestore(&cnt->lock, flags);

+	return ret;

+}

+

 #endif
--

--

Shrinking memory usage at limit change.
Changelog: v1 -> v2

  - adjusted to be based on write_string() patch set

  fixed pointed out styles (below)

  - removed backword goto.

  - removed unneccesary cond_resched().
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
 Documentation/controllers/memory.txt |    3 --

 mm/memcontrol.c                      |   43 +++++++++++++++++++++++++++++++----

 2 files changed, 40 insertions(+), 6 deletions(-)
Index: test-2.6.26-rc8-mm1/mm/memcontrol.c

===================================================================

--- test-2.6.26-rc8-mm1.orig/mm/memcontrol.c

+++ test-2.6.26-rc8-mm1/mm/memcontrol.c

@@ -836,6 +836,26 @@ int mem_cgroup_shrink_usage(struct mm_st

 	return 0;

 }
+int mem_cgroup_resize_limit(struct mem_cgroup *memcg, unsigned long long val)

+{

+

+	int retry_count = MEM_CGROUP_RECLAIM_RETRIES;

+	int progress;

+	int ret = 0;

+

+	while (res_counter_set_limit(&memcg->res, val)) {

+		if (!retry_count) {

+			ret = -EBUSY;

+			break;

+		}

+		progress = try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL);

+		if (!progress)

+			retry_count--;

+	}

+	return ret;

+}

+

+

 /*

  * This routine traverse page_cgroup in given list and drop them all.

  * *And* this routine doesn't reclaim page itself, just removes page_cgroup.

@@ -916,13 +936,29 @@ static u64 mem_cgroup_read(struct cgroup

 	return res_counter_read_u64(&mem_cgroup_from_cont(cont)->res,

 				    cft->private);

 }

-

+/*

+ * The user of this function is...

+ * RES_LIMIT.

+ */

 static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,

 			    const char *buffer)

 {

-	return res_counter_write(&mem_cgroup_from_cont(cont)->res,

-				 cft->private, buffer,

-				 res_counter_memparse_write_strategy);

+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);

+	unsigned long long val;

+	int ret;

+

+        switch (cft->private) {

+	case RES_LIMI...
[ message continues ]

--