From 40e14bd808bbc77a833271abecccf317295ed895 Mon Sep 17 00:00:00 2001
From: Magnus Damm <damm@opensource.se>
Date: Mon, 14 Dec 2009 17:59:49 -0800
Subject: [PATCH] --- yaml --- r: 176309 b: refs/heads/master c:
 c9d0bf241451a3ab7d02e1652c22b80cd7d93e8f h: refs/heads/master i:   176307:
 de94a00e51ab4a0ce688aae18982f7145a562a68 v: v3

---
 [refs]          |  2 +-
 trunk/mm/mmap.c | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index 6ad3f537536c..912e028e7668 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 62c0c2f198c1f2ead05c961e83ef486c45888325
+refs/heads/master: c9d0bf241451a3ab7d02e1652c22b80cd7d93e8f
diff --git a/trunk/mm/mmap.c b/trunk/mm/mmap.c
index 02c09f33df8b..d9c77b2dbe9d 100644
--- a/trunk/mm/mmap.c
+++ b/trunk/mm/mmap.c
@@ -1198,8 +1198,20 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 			goto free_vma;
 	}
 
-	if (vma_wants_writenotify(vma))
+	if (vma_wants_writenotify(vma)) {
+		pgprot_t pprot = vma->vm_page_prot;
+
+		/* Can vma->vm_page_prot have changed??
+		 *
+		 * Answer: Yes, drivers may have changed it in their
+		 *         f_op->mmap method.
+		 *
+		 * Ensures that vmas marked as uncached stay that way.
+		 */
 		vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
+		if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
+			vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	}
 
 	vma_link(mm, vma, prev, rb_link, rb_parent);
 	file = vma->vm_file;