linux-kernel - [PATCH 01/12] cgroups: Add res_counter_write

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Message-Id: <1315267986-28937-2-git-send-email-fweisbec@gmail.com>
Date:	Tue,  6 Sep 2011 02:12:55 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Paul Menage <paul@...lmenage.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Aditya Kali <adityakali@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kay Sievers <kay.sievers@...y.org>,
	Tim Hockin <thockin@...kin.org>, Tejun Heo <tj@...nel.org>
Subject: [PATCH 01/12] cgroups: Add res_counter_write_u64() API

Extend the resource counter API with a mirror of
res_counter_read_u64() to make it handy to update a resource
counter value from a cgroup subsystem u64 value file.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Acked-by: Paul Menage <paul@...lmenage.org>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Aditya Kali <adityakali@...gle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kay Sievers <kay.sievers@...y.org>
Cc: Tim Hockin <thockin@...kin.org>
Cc: Tejun Heo <tj@...nel.org>
---
 include/linux/res_counter.h |    2 ++
 kernel/res_counter.c        |   25 +++++++++++++++++++------
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index c9d625c..1b3fe05 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -82,6 +82,8 @@ int res_counter_memparse_write_strategy(const char *buf,
 int res_counter_write(struct res_counter *counter, int member,
 		      const char *buffer, write_strategy_fn write_strategy);
 
+void res_counter_write_u64(struct res_counter *counter, int member, u64 val);
+
 /*
  * the field descriptors. one for each member of res_counter
  */
diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index 34683ef..0faafcc 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -168,12 +168,26 @@ int res_counter_memparse_write_strategy(const char *buf,
 	return 0;
 }
 
+void res_counter_write_u64(struct res_counter *counter, int member, u64 val)
+{
+	unsigned long long *target;
+	unsigned long flags;
+
+	/*
+	 * We need the lock to protect against concurrent add/dec on 32 bits.
+	 * No need to ifdef it's seldom used.
+	 */
+	spin_lock_irqsave(&counter->lock, flags);
+	target = res_counter_member(counter, member);
+	*target = val;
+	spin_unlock_irqrestore(&counter->lock, flags);
+}
+
 int res_counter_write(struct res_counter *counter, int member,
 		      const char *buf, write_strategy_fn write_strategy)
 {
 	char *end;
-	unsigned long flags;
-	unsigned long long tmp, *val;
+	unsigned long long tmp;
 
 	if (write_strategy) {
 		if (write_strategy(buf, &tmp))
@@ -183,9 +197,8 @@ int res_counter_write(struct res_counter *counter, int member,
 		if (*end != '\0')
 			return -EINVAL;
 	}
-	spin_lock_irqsave(&counter->lock, flags);
-	val = res_counter_member(counter, member);
-	*val = tmp;
-	spin_unlock_irqrestore(&counter->lock, flags);
+
+	res_counter_write_u64(counter, member, tmp);
+
 	return 0;
 }
-- 
1.7.5.4

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