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Subject[PATCH 01/10] cgroups: Add res_counter_write_u64() API
Date
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@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: Andrew Morton <akpm@linux-foundation.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Tim Hockin <thockin@hockin.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Containers <containers@lists.linux-foundation.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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