1 files changed, 25 insertions, 9 deletions

diff --git a/mm/truncate.c b/mm/truncate.c
index ecdfdcc50522..5df947de7654 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -51,15 +51,22 @@ static inline void truncate_partial_page(struct page *page, unsigned partial)
                 do_invalidatepage(page, partial);
 }
 
+/*
+ * This cancels just the dirty bit on the kernel page itself, it
+ * does NOT actually remove dirty bits on any mmap's that may be
+ * around. It also leaves the page tagged dirty, so any sync
+ * activity will still find it on the dirty lists, and in particular,
+ * clear_page_dirty_for_io() will still look at the dirty bits in
+ * the VM.
+ *
+ * Doing this should *normally* only ever be done when a page
+ * is truncated, and is not actually mapped anywhere at all. However,
+ * fs/buffer.c does this when it notices that somebody has cleaned
+ * out all the buffers on a page without actually doing it through
+ * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
+ */
 void cancel_dirty_page(struct page *page, unsigned int account_size)
 {
-        /* If we're cancelling the page, it had better not be mapped any more */
-        if (page_mapped(page)) {
-                static unsigned int warncount;
-
-                WARN_ON(++warncount < 5);
-        }
-                
         if (TestClearPageDirty(page)) {
                 struct address_space *mapping = page->mapping;
                 if (mapping && mapping_cap_account_dirty(mapping)) {
@@ -341,6 +348,15 @@ failed:
         return 0;
 }
 
+static int do_launder_page(struct address_space *mapping, struct page *page)
+{
+        if (!PageDirty(page))
+                return 0;
+        if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
+                return 0;
+        return mapping->a_ops->launder_page(page);
+}
+
 /**
  * invalidate_inode_pages2_range - remove range of pages from an address_space
  * @mapping: the address_space
@@ -405,14 +421,14 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
                                           PAGE_CACHE_SIZE, 0);
                                 }
                         }
-                        if (!invalidate_complete_page2(mapping, page))
+                        ret = do_launder_page(mapping, page);
+                        if (ret == 0 && !invalidate_complete_page2(mapping, page))
                                 ret = -EIO;
                         unlock_page(page);
                 }
                 pagevec_release(&pvec);
                 cond_resched();
         }
-        WARN_ON_ONCE(ret);
         return ret;
 }
 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);