Re: [External] Re: [PATCH 0/3] mm: replace atomic_t with percpu_ref in mempolicy.

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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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