Merge branch 'linus' into x86/x2apic

1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 24843fdd539..59df132cc37 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 */