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Subject[PATCH 3/5] writeback: fix dirtied pages accounting on sub-page writes
When dd in 512bytes, generic_perform_write() calls
balance_dirty_pages_ratelimited() 8 times for the same page, but
obviously the page is only dirtied once.

Fix it by accounting nr_dirtied at page dirty time.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2011-11-17 20:57:13.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-11-17 20:57:15.000000000 +0800
@@ -1224,8 +1224,6 @@ void balance_dirty_pages_ratelimited_nr(
if (bdi->dirty_exceeded)
ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));

- current->nr_dirtied += nr_pages_dirtied;
-
preempt_disable();
/*
* This prevents one CPU to accumulate too many dirtied pages without
@@ -1734,6 +1732,7 @@ void account_page_dirtied(struct page *p
__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
__inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
task_io_account_write(PAGE_CACHE_SIZE);
+ current->nr_dirtied++;
}
}
EXPORT_SYMBOL(account_page_dirtied);



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