From f566f060875f58dba3d8b9e08b51ab5646ef0492 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 20 Aug 2010 16:39:25 -0700
Subject: [PATCH] --- yaml --- r: 209696 b: refs/heads/master c:
 7798330ac8114c731cfab83e634c6ecedaa233d7 h: refs/heads/master v: v3

---
 [refs]           |  2 +-
 trunk/mm/mlock.c | 21 ++++++++++++++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index fb2acf2034bb..fc3cf9691b02 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 297c5eee372478fc32fec5fe8eed711eedb13f3d
+refs/heads/master: 7798330ac8114c731cfab83e634c6ecedaa233d7
diff --git a/trunk/mm/mlock.c b/trunk/mm/mlock.c
index 49e5e4cb8232..cbae7c5b9568 100644
--- a/trunk/mm/mlock.c
+++ b/trunk/mm/mlock.c
@@ -135,6 +135,19 @@ void munlock_vma_page(struct page *page)
 	}
 }
 
+/* Is the vma a continuation of the stack vma above it? */
+static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)
+{
+	return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
+}
+
+static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
+{
+	return (vma->vm_flags & VM_GROWSDOWN) &&
+		(vma->vm_start == addr) &&
+		!vma_stack_continue(vma->vm_prev, addr);
+}
+
 /**
  * __mlock_vma_pages_range() -  mlock a range of pages in the vma.
  * @vma:   target vma
@@ -168,11 +181,9 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
 		gup_flags |= FOLL_WRITE;
 
 	/* We don't try to access the guard page of a stack vma */
-	if (vma->vm_flags & VM_GROWSDOWN) {
-		if (start == vma->vm_start) {
-			start += PAGE_SIZE;
-			nr_pages--;
-		}
+	if (stack_guard_page(vma, start)) {
+		addr += PAGE_SIZE;
+		nr_pages--;
 	}
 
 	while (nr_pages > 0) {