linux-kernel - [PATCH RFC 06/12] mm/gup: Drop folio_fast_pin

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Message-ID: <20231116012908.392077-7-peterx@redhat.com>
Date:   Wed, 15 Nov 2023 20:29:02 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     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>, peterx@...hat.com,
        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>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH RFC 06/12] mm/gup: Drop folio_fast_pin_allowed() in hugepd processing

Hugepd format is only used in PowerPC with hugetlbfs.  In commit
a6e79df92e4a ("mm/gup: disallow FOLL_LONGTERM GUP-fast writing to
file-backed mappings"), we added a check to fail gup-fast if there's
potential risk of violating GUP over writeback file systems.  That should
never apply to hugepd.

Drop that check, not only because it'll never be true for hugepd, but also
it paves way for reusing the function outside fast-gup.

Cc: Lorenzo Stoakes <lstoakes@...il.com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/gup.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 0e00204761d2..424d45e1afb3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2816,11 +2816,6 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 		return 0;
 	}
 
-	if (!folio_fast_pin_allowed(folio, flags)) {
-		gup_put_folio(folio, refs, flags);
-		return 0;
-	}
-
 	if (!pte_write(pte) && gup_must_unshare(NULL, flags, &folio->page)) {
 		gup_put_folio(folio, refs, flags);
 		return 0;
-- 
2.41.0