Re: [PATCH] trivial, memory hotplug: add kswapd_is_running() forbetter readability

[KOSAKI Motohiro]

(6/17/12 9:12 PM), Minchan Kim wrote:
> On 06/17/2012 11:19 AM, David Rientjes wrote:
>
> > On Thu, 14 Jun 2012, Jiang Liu wrote:
> >
> > > diff --git a/include/linux/swap.h b/include/linux/swap.h
> > > index c84ec68..36249d5 100644
> > > --- a/include/linux/swap.h
> > > +++ b/include/linux/swap.h
> > > @@ -301,6 +301,11 @@ static inline void scan_unevictable_unregister_node(struct node *node)
> > >
> > >   extern int kswapd_run(int nid);
> > >   extern void kswapd_stop(int nid);
> > > +static inline bool kswapd_is_running(int nid)
> > > +{
> > > +	return !!(NODE_DATA(nid)->kswapd);
> > > +}
> > > +
> > >   #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > >   extern int mem_cgroup_swappiness(struct mem_cgroup *mem);
> > >   #else
> > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > > index 0d7e3ec..88e479d 100644
> > > --- a/mm/memory_hotplug.c
> > > +++ b/mm/memory_hotplug.c
> > > @@ -522,7 +522,8 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
> > >   	init_per_zone_wmark_min();
> > >
> > >   	if (onlined_pages) {
> > > -		kswapd_run(zone_to_nid(zone));
> > > +		if (!kswapd_is_running(zone_to_nid(zone)))
> > > +			kswapd_run(zone_to_nid(zone));
> > >   		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
> > >   	}
> > >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index 7585101..3dafdbe 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -2941,8 +2941,7 @@ int kswapd_run(int nid)
> > >   	pg_data_t *pgdat = NODE_DATA(nid);
> > >   	int ret = 0;
> > >
> > > -	if (pgdat->kswapd)
> > > -		return 0;
> > > +	BUG_ON(pgdat->kswapd);
> > >
> > >   	pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
> > >   	if (IS_ERR(pgdat->kswapd)) {
> >
> > This isn't better, there's no functional change and you've just added a
> > second conditional for no reason and an unnecessary kswapd_is_running()
> > function.
>
> Tend to agree.
> Now that I think about it, it's enough to add comment.

Ok, I'd like to handle this issue because now I have some mem-hotplug related tirivial
fixes. So, to add one more patch is not big bother to me.



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