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SubjectRe: [PATCH 1/8] cgroups: add res_counter_write_u64() API
On Fri, Jan 13, 2012 at 07:13:47PM +0100, Frederic Weisbecker wrote:
> 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.

I still think it worth to have two versions of res_counter_write_u64().
From my POV, it's clean enough, but consistent with res_counter_read_u64()
and faster on 64bit system.

What do you think?

---
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..aad4ddb 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -167,12 +167,27 @@ 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 flags;
+
+ spin_lock_irqsave(&counter->lock, flags);
+ *res_counter_member(counter, member) = val;
+ spin_unlock_irqrestore(&counter->lock, flags);
+}
+#else
+void res_counter_write_u64(struct res_counter *counter, int member, u64 val)
+{
+ *res_counter_member(counter, member) = 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 +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;
}
--
Kirill A. Shutemov

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