writeback: fix dirtied pages accounting on redirty

[pandora-kernel.git] / mm / page-writeback.c

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 50f0824..ea3f83b 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1800,6 +1800,24 @@ int __set_page_dirty_nobuffers(struct page *page)
 }
 EXPORT_SYMBOL(__set_page_dirty_nobuffers);
 
+/*
+ * Call this whenever redirtying a page, to de-account the dirty counters
+ * (NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied), so that they match the written
+ * counters (NR_WRITTEN, BDI_WRITTEN) in long term. The mismatches will lead to
+ * systematic errors in balanced_dirty_ratelimit and the dirty pages position
+ * control.
+ */
+void account_page_redirty(struct page *page)
+{
+       struct address_space *mapping = page->mapping;
+       if (mapping && mapping_cap_account_dirty(mapping)) {
+               current->nr_dirtied--;
+               dec_zone_page_state(page, NR_DIRTIED);
+               dec_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
+       }
+}
+EXPORT_SYMBOL(account_page_redirty);
+
 /*
  * When a writepage implementation decides that it doesn't want to write this
  * page for some reason, it should redirty the locked page via
@@ -1808,6 +1826,7 @@ EXPORT_SYMBOL(__set_page_dirty_nobuffers);
 int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
 {
        wbc->pages_skipped++;
+       account_page_redirty(page);
        return __set_page_dirty_nobuffers(page);
 }
 EXPORT_SYMBOL(redirty_page_for_writepage);