[PATCH RFC 2/4] mm: Check against orig_pte for finish_fault()

From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Alistair Popple <apopple@nvidia.com>,
	Tiberiu Georgescu <tiberiu.georgescu@nutanix.com>,
	ivan.teterevkov@nutanix.com,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Hugh Dickins <hughd@google.com>,
	peterx@redhat.com, Matthew Wilcox <willy@infradead.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: [PATCH RFC 2/4] mm: Check against orig_pte for finish_fault()
Date: Fri,  6 Aug 2021 23:25:19 -0400	[thread overview]
Message-ID: <20210807032521.7591-3-peterx@redhat.com> (raw)
In-Reply-To: <20210807032521.7591-1-peterx@redhat.com>

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@redhat.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

