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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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