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 tsk->nr_dirtied and bdp_ratelimits at page dirty time.
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 619c445..5d1ef5d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1258,8 +1258,6 @@
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
@@ -1270,12 +1268,9 @@
p = &__get_cpu_var(bdp_ratelimits);
if (unlikely(current->nr_dirtied >= ratelimit))
*p = 0;
- else {
- *p += nr_pages_dirtied;
- if (unlikely(*p >= ratelimit_pages)) {
- *p = 0;
- ratelimit = 0;
- }
+ else if (unlikely(*p >= ratelimit_pages)) {
+ *p = 0;
+ ratelimit = 0;
}
/*
* Pick up the dirtied pages by the exited tasks. This avoids lots of
@@ -1768,6 +1763,8 @@
__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++;
+ this_cpu_inc(bdp_ratelimits);
}
}
EXPORT_SYMBOL(account_page_dirtied);