Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757369Ab2FQCTI (ORCPT ); Sat, 16 Jun 2012 22:19:08 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:33860 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752050Ab2FQCTF (ORCPT ); Sat, 16 Jun 2012 22:19:05 -0400 Date: Sat, 16 Jun 2012 19:19:03 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com 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 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> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2116 Lines: 60 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/