linux-kernel - [PATCH RFC v2 03/12] mm/hugetlb: Don't wait for migration entry during follow page

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Date:   Thu, 17 Nov 2022 20:10:16 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Rik van Riel <riel@...riel.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>, peterx@...hat.com,
        James Houghton <jthoughton@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH RFC v2 03/12] 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 62ff3fc51d4e..61a1fa678172 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6222,7 +6222,6 @@ 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;
@@ -6245,16 +6244,6 @@ 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