mm: protect set_page_dirty() from ongoing truncation

[pandora-kernel.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index d7e497e..c6565f0 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2137,17 +2137,24 @@ reuse:
                if (!dirty_page)
                        return ret;
 
-               /*
-                * Yes, Virginia, this is actually required to prevent a race
-                * with clear_page_dirty_for_io() from clearing the page dirty
-                * bit after it clear all dirty ptes, but before a racing
-                * do_wp_page installs a dirty pte.
-                *
-                * do_shared_fault is protected similarly.
-                */
                if (!page_mkwrite) {
-                       wait_on_page_locked(dirty_page);
-                       set_page_dirty_balance(dirty_page);
+                       struct address_space *mapping;
+                       int dirtied;
+
+                       lock_page(dirty_page);
+                       dirtied = set_page_dirty(dirty_page);
+                       VM_BUG_ON_PAGE(PageAnon(dirty_page), dirty_page);
+                       mapping = dirty_page->mapping;
+                       unlock_page(dirty_page);
+
+                       if (dirtied && mapping) {
+                               /*
+                                * Some device drivers do not set page.mapping
+                                * but still dirty their pages
+                                */
+                               balance_dirty_pages_ratelimited(mapping);
+                       }
+
                        /* file_update_time outside page_lock */
                        if (vma->vm_file)
                                file_update_time(vma->vm_file);