vfs: add/use account_page_dirtied()

Add a helper function account_page_dirtied().  Use that from two
callsites.  reiser4 adds a function which adds a third callsite.

Signed-off-by: Edward Shishkin<edward.shishkin@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 40ca7cd..6aa92b0 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1198,6 +1198,20 @@
 }
 
 /*
+ * Helper function for set_page_dirty family.
+ * NOTE: This relies on being atomic wrt interrupts.
+ */
+void account_page_dirtied(struct page *page, struct address_space *mapping)
+{
+	if (mapping_cap_account_dirty(mapping)) {
+		__inc_zone_page_state(page, NR_FILE_DIRTY);
+		__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
+		task_dirty_inc(current);
+		task_io_account_write(PAGE_CACHE_SIZE);
+	}
+}
+
+/*
  * For address_spaces which do not use buffers.  Just tag the page as dirty in
  * its radix tree.
  *
@@ -1226,13 +1240,7 @@
 		if (mapping2) { /* Race with truncate? */
 			BUG_ON(mapping2 != mapping);
 			WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
-			if (mapping_cap_account_dirty(mapping)) {
-				__inc_zone_page_state(page, NR_FILE_DIRTY);
-				__inc_bdi_stat(mapping->backing_dev_info,
-						BDI_RECLAIMABLE);
-				task_dirty_inc(current);
-				task_io_account_write(PAGE_CACHE_SIZE);
-			}
+			account_page_dirtied(page, mapping);
 			radix_tree_tag_set(&mapping->page_tree,
 				page_index(page), PAGECACHE_TAG_DIRTY);
 		}