Subject: Re: [PATCH v3 2/4] PM: hibernate: make direct map manipulations more explicit

From: Mike Rapoport <[email-masked]>
Date: Tue, 3 Nov 2020 14:13:50 +0200

On Tue, Nov 03, 2020 at 02:08:16PM +0300, Kirill A. Shutemov wrote:
> On Sun, Nov 01, 2020 at 07:08:13PM +0200, Mike Rapoport wrote:
> > diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> > index 46b1804c1ddf..054c8cce4236 100644
> > --- a/kernel/power/snapshot.c
> > +++ b/kernel/power/snapshot.c
> > @@ -76,6 +76,32 @@ static inline void hibernate_restore_protect_page(void *page_address) {}
> >  static inline void hibernate_restore_unprotect_page(void *page_address) {}
> >  #endif /* CONFIG_STRICT_KERNEL_RWX  && CONFIG_ARCH_HAS_SET_MEMORY */
> >  
> > +static inline void hibernate_map_page(struct page *page, int enable)
> > +{
> > +	if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
> > +		unsigned long addr = (unsigned long)page_address(page);
> > +		int ret;
> > +
> > +		/*
> > +		 * This should not fail because remapping a page here means
> > +		 * that we only update protection bits in an existing PTE.
> > +		 * It is still worth to have WARN_ON() here if something
> > +		 * changes and this will no longer be the case.
> > +		 */
> > +		if (enable)
> > +			ret = set_direct_map_default_noflush(page);
> > +		else
> > +			ret = set_direct_map_invalid_noflush(page);
> > +
> > +		if (WARN_ON(ret))
> 
> _ONCE?

I've changed it to pr_warn() after David said people enable panic on
warn in production kernels.

> > +			return;
> > +
> > +		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
> > +	} else {
> > +		debug_pagealloc_map_pages(page, 1, enable);
> > +	}
> > +}
> > +
> >  static int swsusp_page_is_free(struct page *);
> >  static void swsusp_set_page_forbidden(struct page *);
> >  static void swsusp_unset_page_forbidden(struct page *);
> 
> -- 
>  Kirill A. Shutemov

-- 
Sincerely yours,
Mike.