linux-kernel - [PATCH] mm: code improvement of check_stack_guard

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Message-ID: <AANLkTikHHv8j4BOgA36Q16Fn1bh5XMgtzf5LWgY8xNjE@mail.gmail.com>
Date:	Sun, 15 Aug 2010 13:30:17 +0800
From:	jovi zhang <bookjovi@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH] mm: code improvement of check_stack_guard_page function

little code improvement of check_stack_guard_page function.
this commit is on top of commit "mm: keep a guard page below a
grow-down stack segment" of linus.

diff --git a/mm/memory.c b/mm/memory.c
index 9b3b73f..643b112 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2768,13 +2768,15 @@ out_release:
 */
static inline int check_stack_guard_page(struct vm_area_struct *vma,
unsigned long address)
{
-       address &= PAGE_MASK;
-       if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
-               address -= PAGE_SIZE;
-               if (find_vma(vma->vm_mm, address) != vma)
-                       return -ENOMEM;
-
-               expand_stack(vma, address);
+       if (vma->vm_flags & VM_GROWSDOWN) {
+               address &= PAGE_MASK;
+               if(address == vma->vm_start) {
+                       address -= PAGE_SIZE;
+                       if (unlikely(find_vma(vma->vm_mm, address) != vma))
+                               return -ENOMEM;
+
+                       expand_stack(vma, address);
+               }
       }
       return 0;
}