linux-kernel - Re: [PATCH 11/13] mm/treewide: Replace pXd_huge() with pXd

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Message-ID: <20240318161623.GB5825@nvidia.com>
Date: Mon, 18 Mar 2024 13:16:23 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Peter Xu <peterx@...hat.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	Matthew Wilcox <willy@...radead.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"x86@...nel.org" <x86@...nel.org>, Mike Rapoport <rppt@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	"sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>
Subject: Re: [PATCH 11/13] mm/treewide: Replace pXd_huge() with pXd_leaf()

On Thu, Mar 14, 2024 at 08:59:22AM -0400, Peter Xu wrote:

> > > --- a/mm/hmm.c
> > > +++ b/mm/hmm.c
> > > @@ -429,7 +429,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> > >   		return hmm_vma_walk_hole(start, end, -1, walk);
> > >   	}
> > >   
> > > -	if (pud_huge(pud) && pud_devmap(pud)) {
> > > +	if (pud_leaf(pud) && pud_devmap(pud)) {
> > 
> > Didn't previous patch say devmap implies leaf ? Or is it only for GUP ?
> 
> This is an extra safety check that I didn't remove.  Devmap used separate
> bits even though I'm not clear on why.  It should still imply a leaf though.

Yes, something is very wrong if devmap is true on non-leaf..

Jason