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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>
This commit is contained in:
Wu Fengguang 2011-04-14 07:52:37 -06:00
parent 54848d73f9
commit d3bc1fef93
1 changed files with 5 additions and 8 deletions
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13
mm/page-writeback.c
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@ -1258,8 +1258,6 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
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 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
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 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
__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);