Fix up CIFS for "test_clear_page_dirty()" removal

This also adds he required page "writeback" flag handling, that cifs
hasn't been doing and that the page dirty flag changes made obvious.
Acked-by: Steve French <smfltc@us.ibm.com>
Acked-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/cifs/file.c

@@ -1245,14 +1245,21 @@ retry:
 				wait_on_page_writeback(page);
 
 			if (PageWriteback(page) ||
-					!test_clear_page_dirty(page)) {
+					!clear_page_dirty_for_io(page)) {
 				unlock_page(page);
 				break;
 			}
 
+			/*
+			 * This actually clears the dirty bit in the radix tree.
+			 * See cifs_writepage() for more commentary.
+			 */
+			set_page_writeback(page);
+
 			if (page_offset(page) >= mapping->host->i_size) {
 				done = 1;
 				unlock_page(page);
+				end_page_writeback(page);
 				break;
 			}
 
@@ -1316,6 +1323,7 @@ retry:
 					SetPageError(page);
 				kunmap(page);
 				unlock_page(page);
+				end_page_writeback(page);
 				page_cache_release(page);
 			}
 			if ((wbc->nr_to_write -= n_iov) <= 0)
@@ -1352,11 +1360,23 @@ static int cifs_writepage(struct page* page, struct writeback_control *wbc)
         if (!PageUptodate(page)) {
 		cFYI(1, ("ppw - page not up to date"));
 	}
-	
+
+	/*
+	 * Set the "writeback" flag, and clear "dirty" in the radix tree.
+	 *
+	 * A writepage() implementation always needs to do either this,
+	 * or re-dirty the page with "redirty_page_for_writepage()" in
+	 * the case of a failure.
+	 *
+	 * Just unlocking the page will cause the radix tree tag-bits
+	 * to fail to update with the state of the page correctly.
+	 */
+	set_page_writeback(page);		
 	rc = cifs_partialpagewrite(page, 0, PAGE_CACHE_SIZE);
 	SetPageUptodate(page); /* BB add check for error and Clearuptodate? */
 	unlock_page(page);
-	page_cache_release(page);	
+	end_page_writeback(page);
+	page_cache_release(page);
 	FreeXid(xid);
 	return rc;
 }