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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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