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.
>
> More concerning is that online_pages() doesn't check the return value of
> kswapd_run(). We should probably fail the memory hotplug operation that
> onlines a new node and doesn't have a kswapd running and cleanup after
> ourselves in online_pages() with some sane error handling.
Yeb. It's more valuable.
>
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--
Kind regards,
Minchan Kim
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