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Message-ID: <522E92A0.80502@jp.fujitsu.com>
Date: Tue, 10 Sep 2013 12:31:44 +0900
From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To: Toshi Kani <toshi.kani@...com>
CC: <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>, <rjw@...k.pl>,
<kosaki.motohiro@...fujitsu.com>, <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] cpu/mem hotplug: Add try_online_node() for cpu_up()
(2013/09/10 9:24), Toshi Kani wrote:
> cpu_up() has #ifdef CONFIG_MEMORY_HOTPLUG code blocks, which
> call mem_online_node() to put its node online if offlined and
> then call build_all_zonelists() to initialize the zone list.
> These steps are specific to memory hotplug, and should be
> managed in mm/memory_hotplug.c. lock_memory_hotplug() should
> also be held for the whole steps.
>
> For this reason, this patch replaces mem_online_node() with
> try_online_node(), which performs the whole steps with
> lock_memory_hotplug() held. try_online_node() is named after
> try_offline_node() as they have similar purpose.
>
> There is no functional change in this patch.
>
> Signed-off-by: Toshi Kani <toshi.kani@...com>
> ---
> include/linux/memory_hotplug.h | 8 +++++++-
> kernel/cpu.c | 29 +++--------------------------
> mm/memory_hotplug.c | 15 +++++++++++++--
> 3 files changed, 23 insertions(+), 29 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index dd38e62..22203c2 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -94,6 +94,8 @@ extern void __online_page_set_limits(struct page *page);
> extern void __online_page_increment_counters(struct page *page);
> extern void __online_page_free(struct page *page);
>
> +extern int try_online_node(int nid);
> +
> #ifdef CONFIG_MEMORY_HOTREMOVE
> extern bool is_pageblock_removable_nolock(struct page *page);
> extern int arch_remove_memory(u64 start, u64 size);
> @@ -225,6 +227,11 @@ static inline void register_page_bootmem_info_node(struct pglist_data *pgdat)
> {
> }
>
> +static inline int try_online_node(int nid)
> +{
> + return 0;
> +}
> +
> static inline void lock_memory_hotplug(void) {}
> static inline void unlock_memory_hotplug(void) {}
>
> @@ -256,7 +263,6 @@ static inline void remove_memory(int nid, u64 start, u64 size) {}
>
> extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
> void *arg, int (*func)(struct memory_block *, void *));
> -extern int mem_online_node(int nid);
> extern int add_memory(int nid, u64 start, u64 size);
> extern int arch_add_memory(int nid, u64 start, u64 size);
> extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index d7f07a2..c10b285 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -420,11 +420,6 @@ int cpu_up(unsigned int cpu)
> {
> int err = 0;
>
> -#ifdef CONFIG_MEMORY_HOTPLUG
> - int nid;
> - pg_data_t *pgdat;
> -#endif
> -
> if (!cpu_possible(cpu)) {
> printk(KERN_ERR "can't online cpu %d because it is not "
> "configured as may-hotadd at boot time\n", cpu);
> @@ -435,27 +430,9 @@ int cpu_up(unsigned int cpu)
> return -EINVAL;
> }
>
> -#ifdef CONFIG_MEMORY_HOTPLUG
> - nid = cpu_to_node(cpu);
> - if (!node_online(nid)) {
> - err = mem_online_node(nid);
> - if (err)
> - return err;
> - }
> -
> - pgdat = NODE_DATA(nid);
> - if (!pgdat) {
> - printk(KERN_ERR
> - "Can't online cpu %d due to NULL pgdat\n", cpu);
Please move this comments into try_online_node() too.
Thanks,
Yasuaki Ishimatsu
> - return -ENOMEM;
> - }
> -
> - if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
> - mutex_lock(&zonelists_mutex);
> - build_all_zonelists(NULL, NULL);
> - mutex_unlock(&zonelists_mutex);
> - }
> -#endif
> + err = try_online_node(cpu_to_node(cpu));
> + if (err)
> + return err;
>
> cpu_maps_update_begin();
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index ed85fe3..c326bdf 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1044,14 +1044,19 @@ static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
> }
>
>
> -/*
> +/**
> + * try_online_node - online a node if offlined
> + *
> * called by cpu_up() to online a node without onlined memory.
> */
> -int mem_online_node(int nid)
> +int try_online_node(int nid)
> {
> pg_data_t *pgdat;
> int ret;
>
> + if (node_online(nid))
> + return 0;
> +
> lock_memory_hotplug();
> pgdat = hotadd_new_pgdat(nid, 0);
> if (!pgdat) {
> @@ -1062,6 +1067,12 @@ int mem_online_node(int nid)
> ret = register_one_node(nid);
> BUG_ON(ret);
>
> + if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
> + mutex_lock(&zonelists_mutex);
> + build_all_zonelists(NULL, NULL);
> + mutex_unlock(&zonelists_mutex);
> + }
> +
> out:
> unlock_memory_hotplug();
> return ret;
>
> --
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