Le lundi 13 dÃcembre 2010 Ã 13:42 +1100, Nick Piggin a Ãcrit :
> + */
> +static inline void add_mnt_count(struct vfsmount *mnt, int n)
maybe name it __add_mnt_count() (should be called with preempt off)
> +{
> +#ifdef CONFIG_SMP
> + (*per_cpu_ptr(mnt->mnt_count, smp_processor_id())) += n;
__this_cpu_add(mnt->mnt_count, n);
> +#else
> + mnt->mnt_count += n;
> +#endif
> +}
and define a preempt safe version :
static inline void __add_mnt_count(struct vfsmount *mnt, int n)
{
#ifdef CONFIG_SMP
__this_cpu_add(mnt->mnt_count, n);
#else
mnt->mnt_count += n;
#endif
}
static inline void add_mnt_count(struct vfsmount *mnt, int n)
{
#ifdef CONFIG_SMP
this_cpu_add(mnt->mnt_count, n);
#else
preempt_disable();
mnt->mnt_count += n;
preempt_enable();
#endif
}
> +
> +static inline void set_mnt_count(struct vfsmount *mnt, int n)
> +{
> +#ifdef CONFIG_SMP
> + preempt_disable();
> + (*per_cpu_ptr(mnt->mnt_count, smp_processor_id())) = n;
> + preempt_enable();
last 3 lines can be replaced by :
this_cpu_write(mnt->mnt_count, n);
> +#else
> + mnt->mnt_count = n;
> +#endif
> +}
> +
> #ifdef CONFIG_SMP
> int __percpu *mnt_writers;
> + int __percpu *mnt_count;
> #else
> int mnt_writers;
> + int mnt_count;
> #endif
You could use a struct and one per cpu allocation to use one cache line
for both objects :
struct mnt_counters {
int writers;
int count;
};
...
#ifdef CONFIG_SMP
struct mnt_counters __percpu *mnt_counters;
#else
struct mnt_counters mnt_counters;
#endif
This would use one pointer instead of two in SMP
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
