linux-kernel - [PATCH] mm/gup: Check for protnone only if it is a PTE entry.

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Message-Id: <1487498326-8734-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
Date:   Sun, 19 Feb 2017 15:28:46 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     akpm@...ux-foundation.org, Rik van Riel <riel@...riel.com>,
        Mel Gorman <mgorman@...hsingularity.net>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH] mm/gup: Check for protnone only if it is a PTE entry.

Do the prot_none/FOLL_NUMA check after we are sure this is a THP pte. Archs
can implement prot_none such that it can return true for regular pmd entries.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 mm/gup.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 55315555489d..bb5f3d69f87e 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -265,8 +265,6 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
 			return page;
 		return no_page_table(vma, flags);
 	}
-	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
-		return no_page_table(vma, flags);
 	if (pmd_devmap(*pmd)) {
 		ptl = pmd_lock(mm, pmd);
 		page = follow_devmap_pmd(vma, address, pmd, flags);
@@ -277,6 +275,9 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
 	if (likely(!pmd_trans_huge(*pmd)))
 		return follow_page_pte(vma, address, pmd, flags);
 
+	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
+		return no_page_table(vma, flags);
+
 	ptl = pmd_lock(mm, pmd);
 	if (unlikely(!pmd_trans_huge(*pmd))) {
 		spin_unlock(ptl);
-- 
2.7.4