linux-kernel - [PATCH v2 02/10] mm/hugetlb: Don't wait for migration entry during follow page

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Message-Id: <20221207203034.650899-3-peterx@redhat.com>
Date:   Wed,  7 Dec 2022 15:30:26 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Muchun Song <songmuchun@...edance.com>,
        John Hubbard <jhubbard@...dia.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        James Houghton <jthoughton@...gle.com>,
        Jann Horn <jannh@...gle.com>, Rik van Riel <riel@...riel.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>, peterx@...hat.com,
        David Hildenbrand <david@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>
Subject: [PATCH v2 02/10] mm/hugetlb: Don't wait for migration entry during follow page

That's what the code does with !hugetlb pages, so we should logically do
the same for hugetlb, so migration entry will also be treated as no page.

This is probably also the last piece in follow_page code that may sleep,
the last one should be removed in cf994dd8af27 ("mm/gup: remove
FOLL_MIGRATION", 2022-11-16).

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/hugetlb.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1088f2f41c88..c8a6673fe5b4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6232,7 +6232,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
 	if (WARN_ON_ONCE(flags & FOLL_PIN))
 		return NULL;
 
-retry:
 	pte = huge_pte_offset(mm, haddr, huge_page_size(h));
 	if (!pte)
 		return NULL;
@@ -6255,16 +6254,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
 			page = NULL;
 			goto out;
 		}
-	} else {
-		if (is_hugetlb_entry_migration(entry)) {
-			spin_unlock(ptl);
-			__migration_entry_wait_huge(pte, ptl);
-			goto retry;
-		}
-		/*
-		 * hwpoisoned entry is treated as no_page_table in
-		 * follow_page_mask().
-		 */
 	}
 out:
 	spin_unlock(ptl);
-- 
2.37.3