Re: [PATCH] pagemap: Add alert to mapping_set_release_always() for mapping with no release_folio

[Deepak Karn]

On Thu, Dec 11, 2025 at 2:53 PM Jan Kara <jack@xxxxxxx> wrote:
>
> On Wed 10-12-25 21:36:43, Matthew Wilcox wrote:
> > On Thu, Dec 11, 2025 at 01:31:04AM +0530, Deepakkumar Karn wrote:
> > >  static inline void mapping_set_release_always(struct address_space *mapping)
> > >  {
> > > +   /* Alert while setting the flag with no release_folio callback */
> >
> > The comment is superfluous.
>
> Agreed.
>
> > > +   VM_WARN_ONCE(!mapping->a_ops->release_folio,
> > > +                "Setting AS_RELEASE_ALWAYS with no release_folio");
> >
> > But you haven't said why we need to do this.  Surely the NULL pointer
> > splat is enough to tell you that you did something stupid?
>
> Well, but this will tell it much earlier and it will directly point to the
> place were you've done the mistake (instead of having to figure out why
> drop_buffers() is crashing on you). So I think this assert makes sense to
> ease debugging and as kind of self-reminding documentation :).
>

Thank you Jan for your response, as you highlighted adding this change will help
with early warning, making it immediately clear during filesystem
initialization.
Also as Matthew stated, the comment is superfluous and doesn't serve
any purpose.
I will remove that comment in another version.

Regards,
Deepakkumar Karn