Re: [PATCH] files: rcu free files_struct

[Paul E. McKenney]

On Wed, Dec 09, 2020 at 03:29:09PM -0800, Linus Torvalds wrote:
> On Wed, Dec 9, 2020 at 3:07 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> >
> >  #. It is not necessary to use rcu_assign_pointer() when creating
> >     linked structures that are to be published via a single external
> > -   pointer. The RCU_INIT_POINTER() macro is provided for this task
> > -   and also for assigning ``NULL`` pointers at runtime.
> > +   pointer. The RCU_INIT_POINTER() macro is provided for this task.
> > +   It used to be more efficient to use RCU_INIT_POINTER() to store a
> > +   ``NULL`` pointer, but rcu_assign_pointer() now optimises for a constant
> > +   ``NULL`` pointer itself.
> 
> I would just remove the historical note about "It used to be more
> efficient ..". It's not really helpful.
> 
> If somebody wants to dig into the history, it's there in git.
> 
> Maybe the note could be part of the commit message for the comment
> update, explaining that it used to be more efficient but no longer is.
> Because commit messages are about the explanation for the change.
> 
> But I don't feel it makes any sense in the source code.

Like this, then?

							Thanx, Paul

 #. It is not necessary to use rcu_assign_pointer() when creating
    linked structures that are to be published via a single external
-   pointer. The RCU_INIT_POINTER() macro is provided for this task
-   and also for assigning ``NULL`` pointers at runtime.
+   pointer. The RCU_INIT_POINTER() macro is provided for this task.