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SubjectRe: [PATCH 01/10] cgroups: Add res_counter_write_u64() API
On Mon, Oct 03, 2011 at 09:07:03PM +0200, 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.
>
> 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.
> + */

Should we hace two version of res_counter_write_u64() for 32/64 bit host?
As with res_counter_read_u64().

> + 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
>

--
Kirill A. Shutemov


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