linux-kernel - Re: [PATCH v3 3/7] x86: Stop calling page_address() in free

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Message-ID: <aLslu1yKPNgoz1OU@fedora>
Date: Fri, 5 Sep 2025 11:02:35 -0700
From: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-block@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
	linux-efi@...r.kernel.org, virtualization@...ts.linux.dev,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 3/7] x86: Stop calling page_address() in free_pages()

On Thu, Sep 04, 2025 at 02:54:24PM +0300, Mike Rapoport wrote:
> On Thu, Sep 04, 2025 at 02:51:14PM +0300, Mike Rapoport wrote:
> > On Wed, Sep 03, 2025 at 11:59:17AM -0700, Vishal Moola (Oracle) wrote:
> > > free_pages() should be used when we only have a virtual address. We
> > > should call __free_pages() directly on our page instead.
> > > 
> > > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
> > > Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
> > > ---
> > >  arch/x86/mm/init_64.c          | 2 +-
> > >  arch/x86/platform/efi/memmap.c | 2 +-
> > >  2 files changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > > index b9426fce5f3e..0e4270e20fad 100644
> > > --- a/arch/x86/mm/init_64.c
> > > +++ b/arch/x86/mm/init_64.c
> > > @@ -1031,7 +1031,7 @@ static void __meminit free_pagetable(struct page *page, int order)
> > >  		free_reserved_pages(page, nr_pages);
> > >  #endif
> > >  	} else {
> > > -		free_pages((unsigned long)page_address(page), order);
> > > +		__free_pages(page, order);
> > >  	}
> > >  }
> > >  
> > > diff --git a/arch/x86/platform/efi/memmap.c b/arch/x86/platform/efi/memmap.c
> > > index 061b8ecc71a1..023697c88910 100644
> > > --- a/arch/x86/platform/efi/memmap.c
> > > +++ b/arch/x86/platform/efi/memmap.c
> > > @@ -42,7 +42,7 @@ void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
> > >  		struct page *p = pfn_to_page(PHYS_PFN(phys));
> > >  		unsigned int order = get_order(size);
> > >  
> > > -		free_pages((unsigned long) page_address(p), order);
> > 
> > Could be just free_pages((unsigned long)phys_to_virt(phys), order), then
> > the page is not needed at all.
> 
> Or even __free_pages(phys_to_page(phys), order);

Right. It actually looks like we could inline this whole block if we
really wanted to...

__free_pages(phys_to_page(phys), get_order(size));

Should I send a fixup (or v4) with this change?