[PATCH 1/2][-mm][resend] res_counter limit change support ebusy

[KAMEZAWA Hiroyuki]

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.

This is an enhancement.
named as res_counter-limit-change-ebusy.patch

Changelog:
  - fixed white space bug.

Acked-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Acked-by: Pavel Emelyanov <xemul@xxxxxxxxxx>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>


 include/linux/res_counter.h |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

Index: linux-2.6.26-rc8-mm1/include/linux/res_counter.h
===================================================================
--- linux-2.6.26-rc8-mm1.orig/include/linux/res_counter.h
+++ linux-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

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