linux-kernel - Re: [PATCH RFC 09/12] mm/gup: Handle huge pud for follow_pud

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Date:   Thu, 23 Nov 2023 11:19:32 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Mike Kravetz <mike.kravetz@...cle.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Rapoport <rppt@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        James Houghton <jthoughton@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC 09/12] mm/gup: Handle huge pud for follow_pud_mask()

On Wed, Nov 22, 2023 at 11:28:31PM -0800, Christoph Hellwig wrote:
> > We need to export "struct follow_page_context" along the way, so that
> > huge_memory.c can understand it.
> 
> Again, thankfully not actually exported, just made global.

In the new version that shouldn't be needed, because I just noticed
huge_memory.c is only compiled with THP=on.  Logically it may start to make
sense at some point to have thp.c for THP=on, and huge_memory.c for THP ||
HUGETLB.  But I'd rather leave that done separately even if so..

In short, for this one, I'll drop that in the commit message, as I'll leave
"struct follow_page_context" alone.

> 
> > @@ -751,24 +746,25 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
> >  				    unsigned int flags,
> >  				    struct follow_page_context *ctx)
> >  {
> > -	pud_t *pud;
> > +	pud_t *pudp, pud;
> 
> This adding of pud while useful seems mostly unrelated and clutter
> the patch up quite a bit.  If you have to respin this anyway it might
> be worth to split it out into a little prep patch.

I can do this.  I'll also try to do the same for the rest patches, if
applicable.

Thanks,

-- 
Peter Xu