From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id 2C7A76B004D for ; Sat, 16 Jun 2012 22:19:06 -0400 (EDT) Received: by dakp5 with SMTP id p5so6826532dak.14 for ; Sat, 16 Jun 2012 19:19:05 -0700 (PDT) Date: Sat, 16 Jun 2012 19:19:03 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH] trivial, memory hotplug: add kswapd_is_running() for better readability In-Reply-To: <1339663776-196-1-git-send-email-jiang.liu@huawei.com> Message-ID: References: <4FD97718.6060008@kernel.org> <1339663776-196-1-git-send-email-jiang.liu@huawei.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Jiang Liu Cc: Minchan Kim , Keping Chen , Mel Gorman , KOSAKI Motohiro , KAMEZAWA Hiroyuki , Andrew Morton , Hugh Dickins , Tony Luck , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jiang Liu 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. 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org