---

yaml --- r: 230724 b: refs/heads/master c: 5ecfda0 h: refs/heads/master v: v3
git-mirror · Jan 14, 2011 · b1c3fa1 · b1c3fa1
1 parent a7d9ec7
commit b1c3fa1
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Showing 3 changed files with 13 additions and 3 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 72ddc8f72270758951ccefb7d190f364d20215ab
+refs/heads/master: 5ecfda041e4b4bd858d25bbf5a16c2a6c06d7272
diff --git a/trunk/mm/memory.c b/trunk/mm/memory.c
@@ -3299,7 +3299,12 @@ int make_pages_present(unsigned long addr, unsigned long end)
 	vma = find_vma(current->mm, addr);
 	if (!vma)
 		return -ENOMEM;
-	write = (vma->vm_flags & VM_WRITE) != 0;
+	/*
+	 * We want to touch writable mappings with a write fault in order
+	 * to break COW, except for shared mappings because these don't COW
+	 * and we would not want to dirty them for nothing.
+	 */
+	write = (vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE;
 	BUG_ON(addr >= end);
 	BUG_ON(end > vma->vm_end);
 	len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;

diff --git a/trunk/mm/mlock.c b/trunk/mm/mlock.c
@@ -171,7 +171,12 @@ static long __mlock_vma_pages_range(struct vm_area_struct *vma,
 	VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
 
 	gup_flags = FOLL_TOUCH | FOLL_GET;
-	if (vma->vm_flags & VM_WRITE)
+	/*
+	 * We want to touch writable mappings with a write fault in order
+	 * to break COW, except for shared mappings because these don't COW
+	 * and we would not want to dirty them for nothing.
+	 */
+	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
 		gup_flags |= FOLL_WRITE;
 
 	/* We don't try to access the guard page of a stack vma */