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

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Date:   Tue, 29 Nov 2022 14:35:18 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     James Houghton <jthoughton@...gle.com>,
        Jann Horn <jannh@...gle.com>, peterx@...hat.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        David Hildenbrand <david@...hat.com>
Subject: [PATCH 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).

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 9d97c9a2a15d..dfe677fadaf8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6234,7 +6234,6 @@ 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;
@@ -6257,16 +6256,6 @@ 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