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Message-ID: <7cd1db3f-9bdf-dc0b-692c-380a2fa14286@redhat.com>
Date: Tue, 20 Jun 2023 17:28:28 +0200
From: David Hildenbrand <david@...hat.com>
To: Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Mike Rapoport <rppt@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
John Hubbard <jhubbard@...dia.com>,
"Kirill A . Shutemov" <kirill@...temov.name>,
James Houghton <jthoughton@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Lorenzo Stoakes <lstoakes@...il.com>,
Hugh Dickins <hughd@...gle.com>,
Mike Kravetz <mike.kravetz@...cle.com>,
Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v2 2/8] mm/hugetlb: Prepare hugetlb_follow_page_mask() for
FOLL_PIN
On 20.06.23 01:10, Peter Xu wrote:
> follow_page() doesn't use FOLL_PIN, meanwhile hugetlb seems to not be the
> target of FOLL_WRITE either. However add the checks.
>
> Namely, either the need to CoW due to missing write bit, or proper CoR on
> !AnonExclusive pages over R/O pins to reject the follow page. That brings
> this function closer to follow_hugetlb_page().
>
> So we don't care before, and also for now. But we'll care if we switch
> over slow-gup to use hugetlb_follow_page_mask(). We'll also care when to
> return -EMLINK properly, as that's the gup internal api to mean "we should
> do CoR". Not really needed for follow page path, though.
>
> When at it, switching the try_grab_page() to use WARN_ON_ONCE(), to be
> clear that it just should never fail.
Oh, and does this comment really belong into this patch or am I confused?
--
Cheers,
David / dhildenb
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