1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 24843fdd5395..59df132cc375 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -74,6 +74,7 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
 {
         struct fb_info *info = vma->vm_private_data;
         struct fb_deferred_io *fbdefio = info->fbdefio;
+        struct page *cur;
 
         /* this is a callback we get when userspace first tries to
         write to the page. we schedule a workqueue. that workqueue
@@ -83,7 +84,24 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
 
         /* protect against the workqueue changing the page list */
         mutex_lock(&fbdefio->lock);
-        list_add(&page->lru, &fbdefio->pagelist);
+
+        /* we loop through the pagelist before adding in order
+        to keep the pagelist sorted */
+        list_for_each_entry(cur, &fbdefio->pagelist, lru) {
+                /* this check is to catch the case where a new
+                process could start writing to the same page
+                through a new pte. this new access can cause the
+                mkwrite even when the original ps's pte is marked
+                writable */
+                if (unlikely(cur == page))
+                        goto page_already_added;
+                else if (cur->index > page->index)
+                        break;
+        }
+
+        list_add_tail(&page->lru, &cur->lru);
+
+page_already_added:
         mutex_unlock(&fbdefio->lock);
 
         /* come back after delay to process the deferred IO */