Re: [PATCH 3/5] writeback: fix dirtied pages accounting onsub-page writes

[Wu Fengguang]

> > @@ -1743,6 +1738,8 @@ void account_page_dirtied(struct page *p
> >  		__inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
> >  		task_dirty_inc(current);
> >  		task_io_account_write(PAGE_CACHE_SIZE);
> > +		current->nr_dirtied++;
> > +		__get_cpu_var(bdp_ratelimits)++;
>   I think you need preempt_disable() and preempt_enable() pair around
> __get_cpu_var(). Otherwise a process could get rescheduled in the middle of
> read-modify-write cycle...

Hmm, I'm not worried about it at all, because bdp_ratelimits don't
need to be accurate. In normal cases it won't even trigger one single
call to balance_dirty_pages().

btw, account_page_dirtied() is called inside spinlock, will it be
sufficient?

Thanks,
Fengguang
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