linux-kernel - [PATCH RFC 2/4] mm: Check against orig_pte for finish

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Date:   Fri,  6 Aug 2021 23:25:19 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Alistair Popple <apopple@...dia.com>,
        Tiberiu Georgescu <tiberiu.georgescu@...anix.com>,
        ivan.teterevkov@...anix.com,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Hugh Dickins <hughd@...gle.com>, peterx@...hat.com,
        Matthew Wilcox <willy@...radead.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH RFC 2/4] mm: Check against orig_pte for finish_fault()

We used to check against none pte and in those cases orig_pte should always be
none pte anyway.

This change prepares us to be able to call do_fault() on !none ptes.  For
example, we should allow that to happen for pte marker that has PAGEOUT set.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 25fc46e87214..7288f585544a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4047,7 +4047,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 				      vmf->address, &vmf->ptl);
 	ret = 0;
 	/* Re-check under ptl */
-	if (likely(pte_none(*vmf->pte)))
+	if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
 		do_set_pte(vmf, page, vmf->address);
 	else
 		ret = VM_FAULT_NOPAGE;
-- 
2.32.0