[PATCH 01/10] cgroups: add res_counter_write_u64() API

[Frederic Weisbecker <fweisbec@gmail.com>]

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.

[kirill@shutemov.name: Separate 32 bits and 64 bits versions]

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Menage <paul@paulmenage.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Aditya Kali <adityakali@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tim Hockin <thockin@hockin.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Containers <containers@lists.linux-foundation.org>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Cgroups <cgroups@vger.kernel.org>
Cc: Daniel J Walsh <dwalsh@redhat.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Max Kellermann <mk@cm4all.com>
Cc: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
---
 include/linux/res_counter.h |    2 ++
 kernel/res_counter.c        |   31 +++++++++++++++++++++++++------
 2 files changed, 27 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 6d269cc..c46465c 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -167,12 +167,32 @@ int res_counter_memparse_write_strategy(const char *buf,
 	return 0;
 }
 
+#if BITS_PER_LONG == 32
+void res_counter_write_u64(struct res_counter *counter, int member, u64 val)
+{
+	unsigned long long *target;
+	unsigned long flags;
+
+	spin_lock_irqsave(&counter->lock, flags);
+	target = res_counter_member(counter, member);
+	*target = val;
+	spin_unlock_irqrestore(&counter->lock, flags);
+}
+#else
+void res_counter_write_u64(struct res_counter *counter, int member, u64 val)
+{
+	unsigned long long *target;
+
+	target = res_counter_member(counter, member);
+	*target = val;
+}
+#endif
+
 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))
@@ -182,9 +202,8 @@ 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