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SubjectRe: [External] Re: [PATCH 0/3] mm: replace atomic_t with percpu_ref in mempolicy.
From
> On Mon 05-12-22 00:14:29, Zhongkun He wrote:
> [...]
>> +/* Obtain a reference on the specified mpol */
>> static inline void mpol_get(struct mempolicy *pol)
>> {
>> if (pol)
>
> Shouldn't this be mpol_needs_cond_ref?
>
>> - atomic_inc(&pol->refcnt);
>> + percpu_ref_get(&pol->refcnt);
>> +}
>> +
>> +static inline bool mpol_tryget(struct mempolicy *pol)
>> +{
>> + return pol && percpu_ref_tryget(&pol->refcnt);
>> }
>>
>> +/*
>> + * This function initiates destruction of mempolicy.
>
> This is not a useful comment. It would be much more helpful to say when
> this should be called.
>
>> + */
>> +static inline void mpol_kill(struct mempolicy *pol)
>> +{
>> + if (pol)
>> + percpu_ref_kill(&pol->refcnt);
>> +}
>> +
>> +
>> extern bool __mpol_equal(struct mempolicy *a, struct mempolicy *b);
>> static inline bool mpol_equal(struct mempolicy *a, struct mempolicy *b)
>> {
>> @@ -197,11 +210,15 @@ static inline void mpol_put(struct mempolicy *p)
>> {
>> }
>>
>> -static inline void mpol_cond_put(struct mempolicy *pol)
>> +static inline void mpol_get(struct mempolicy *pol)
>> {
>> }
>>
>> -static inline void mpol_get(struct mempolicy *pol)
>> +static inline bool mpol_tryget(struct mempolicy *pol)
>> +{
>> +}
>
> This should return false, right?
>
> [...]
>> +/* Obtain a reference on the specified task mempolicy */
>
> Again, this is pretty much clear from the name. It would be more useful
> to explain how the pointer can be used - e.g. needs to call mpol_put
> or mpol_kill depending on the calling context.
>
>> +static mempolicy *get_task_mpol(struct task_struct *p)
>> +{
>> + struct mempolicy *pol;
>> +
>> + rcu_read_lock();
>> + pol = rcu_dereference(p->mempolicy);
>> +
>> + if (!pol || mpol_tryget(pol))
>
> Shouldn't be !mpol_tryget?
>
>> + pol = NULL;
>> + rcu_read_unlock();
>> +
>> + return pol;
>> +}
>> +
>
> I do not see any rcu_assign_pointer for the newly created policy so this
> seems incomplete. Ditto no mpol_kill calls. I am unlikely to get into
> follow up patches now. Please split up the work so that it is reviewable
> more easily and then I can have a further look.
>
> Thanks!

Thanks for your review, some changes may be in other patch,i will
reorganize the patches according to the suggestions to make
things clear.

Thanks.

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