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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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