fb_defio: fix for non-dirty ptes
[linux-2.6.git] / drivers / video / fb_defio.c
index 6113c47..1105a59 100644 (file)
@@ -155,25 +155,41 @@ static void fb_deferred_io_work(struct work_struct *work)
 {
        struct fb_info *info = container_of(work, struct fb_info,
                                                deferred_work.work);
-       struct list_head *node, *next;
-       struct page *cur;
        struct fb_deferred_io *fbdefio = info->fbdefio;
+       struct page *page, *tmp_page;
+       struct list_head *node, *tmp_node;
+       struct list_head non_dirty;
+
+       INIT_LIST_HEAD(&non_dirty);
 
        /* here we mkclean the pages, then do all deferred IO */
        mutex_lock(&fbdefio->lock);
-       list_for_each_entry(cur, &fbdefio->pagelist, lru) {
-               lock_page(cur);
-               page_mkclean(cur);
-               unlock_page(cur);
+       list_for_each_entry_safe(page, tmp_page, &fbdefio->pagelist, lru) {
+               lock_page(page);
+               /*
+                * The workqueue callback can be triggered after a
+                * ->page_mkwrite() call but before the PTE has been marked
+                * dirty. In this case page_mkclean() won't "rearm" the page.
+                *
+                * To avoid this, remove those "non-dirty" pages from the
+                * pagelist before calling the driver's callback, then add
+                * them back to get processed on the next work iteration.
+                * At that time, their PTEs will hopefully be dirty for real.
+                */
+               if (!page_mkclean(page))
+                       list_move_tail(&page->lru, &non_dirty);
+               unlock_page(page);
        }
 
        /* driver's callback with pagelist */
        fbdefio->deferred_io(info, &fbdefio->pagelist);
 
-       /* clear the list */
-       list_for_each_safe(node, next, &fbdefio->pagelist) {
+       /* clear the list... */
+       list_for_each_safe(node, tmp_node, &fbdefio->pagelist) {
                list_del(node);
        }
+       /* ... and add back the "non-dirty" pages to the list */
+       list_splice_tail(&non_dirty, &fbdefio->pagelist);
        mutex_unlock(&fbdefio->lock);
 }
 
@@ -202,6 +218,7 @@ EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 void fb_deferred_io_cleanup(struct fb_info *info)
 {
        struct fb_deferred_io *fbdefio = info->fbdefio;
+       struct list_head *node, *tmp_node;
        struct page *page;
        int i;
 
@@ -209,6 +226,13 @@ void fb_deferred_io_cleanup(struct fb_info *info)
        cancel_delayed_work(&info->deferred_work);
        flush_scheduled_work();
 
+       /*  the list may have still some non-dirty pages at this point */
+       mutex_lock(&fbdefio->lock);
+       list_for_each_safe(node, tmp_node, &fbdefio->pagelist) {
+               list_del(node);
+       }
+       mutex_unlock(&fbdefio->lock);
+
        /* clear out the mapping that we setup */
        for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
                page = fb_deferred_io_page(info, i);