linux-kernel - [PATCH] mm: honor FOLL_GET flag in follow_hugetlb

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Date:	Tue,  7 May 2013 18:58:42 -0400
From:	j.glisse@...il.com
To:	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, Jerome Glisse <jglisse@...hat.com>
Subject: [PATCH] mm: honor FOLL_GET flag in follow_hugetlb_page v2

From: Jerome Glisse <jglisse@...hat.com>

Do not increase page count if FOLL_GET is not set. None of the
current user can trigger the issue because none of the current
user call __get_user_pages with both the pages array ptr non
NULL and the FOLL_GET flags non set in other word all caller
of __get_user_pages that don't set the FOLL_GET flags also call
with pages == NULL.

v2: Do not use get_page_foll. Improved comment.

Signed-off-by: Jerome Glisse <jglisse@...hat.com>
---
 mm/hugetlb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ca9a7c6..32f323b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2981,7 +2981,9 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 same_page:
 		if (pages) {
 			pages[i] = mem_map_offset(page, pfn_offset);
-			get_page(pages[i]);
+			if (flags & FOLL_GET) {
+				get_page(pages[i]);
+			}
 		}
 
 		if (vmas)
-- 
1.7.11.7

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