Re: [PATCH V8 40/44] memremap_pages: Add pgmap_protection_flag_invalid()

Ira Weiny
2022-03-02T02:01:09Z

On Mon, Jan 31, 2022 at 05:37:17PM -0800, Edgecombe, Rick P wrote:
> On Thu, 2022-01-27 at 09:55 -0800, ira.weiny@intel.com wrote:
> > +/*
> > + * pgmap_protection_flag_invalid - Check and flag an invalid use of
> > a pgmap
> > + * protected page
> > + *
> > + * There are code paths which are known to not be compatible with
> > pgmap
> > + * protections.
>
> This could get hopefully get stale. Maybe the comment should just
> describe what the function does and leave this reasoning to the commit
> log?

Thanks for the review but based on the thread with Dan this patch is dropped.

Thanks,
Ira

>
> > pgmap_protection_flag_invalid() is provided as a 'relief
> > + * valve' to be used in those functions which are known to be
> > incompatible.
> > + *
> > + * Thus an invalid use case can be flaged with more precise data
> > rather than
> > + * just flagging a fault. Like the fault handler code this abandons
>
> In the commit log you called this "the invalid access on fault" and it
> seemed a little clearer to me then "just flagging a fault".
>
> > the use of
> > + * the PKS key and optionally allows the calling code path to
> > continue based on
> > + * the configuration of the memremap.pks_fault_mode command line
> > + * (and/or sysfs) option.
>
> It lets the calling code continue regardless right? It just warns if
> !PKS_MODE_STRICT. Why not warn in the case of PKS_MODE_STRICT too?
>
> Seems surprising that the stricter setting would have less checks.
>
> > + */
> > +static inline void pgmap_protection_flag_invalid(struct page *page)
> > +{
> > + if (!pgmap_check_pgmap_prot(page))
> > + return;
> > + __pgmap_protection_flag_invalid(page->pgmap);
> > +}