linux-kernel - Re: [PATCH v2] mm/memory: Don't require head page for do_set

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Date: Tue, 11 Jun 2024 11:21:31 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: Andrew Bresticker <abrestic@...osinc.com>, David Hildenbrand
 <david@...hat.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/memory: Don't require head page for do_set_pmd()

On Tue, 11 Jun 2024 19:03:29 +0100 Matthew Wilcox <willy@...radead.org> wrote:

> On Tue, Jun 11, 2024 at 08:32:16AM -0700, Andrew Bresticker wrote:
> > -	if (page != &folio->page || folio_order(folio) != HPAGE_PMD_ORDER)
> > +	if (folio_order(folio) != HPAGE_PMD_ORDER)
> >  		return ret;
> > +	page = &folio->page;
> 
> This works today, but in about six months time it's going to be a pain.
> 
> +	page = folio_page(folio, 0);
> 
> is the one which works today and in the future.

I was wondering about that.

hp2:/usr/src/25> fgrep "&folio->page" mm/*.c | wc -l
84
hp2:/usr/src/25> fgrep "folio_page(" mm/*.c | wc -l 
35

Should these all be converted?  What's the general rule here?