Message-ID: <ba5f460b-fc6c-601b-053c-086185fd3049@redhat.com>
Date:   Mon, 13 Dec 2021 16:07:18 +0100
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Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages
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To:     Michal Hocko <mhocko@suse.com>,
        Alexey Makhalov <amakhalov@vmware.com>
Cc:     Dennis Zhou <dennis@kernel.org>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.de>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Nico Pache <npache@redhat.com>
References: <2e191db3-286f-90c6-bf96-3f89891e9926@gmail.com>
 <YYqstfX8PSGDfWsn@dhcp22.suse.cz> <YYrGpn/52HaLCAyo@fedora>
 <YYrSC7vtSQXz652a@dhcp22.suse.cz>
 <BAE95F0C-FAA7-40C6-A0D6-5049B1207A27@vmware.com>
 <YZN3ExwL7BiDS5nj@dhcp22.suse.cz>
 <5239D699-523C-4F0C-923A-B068E476043E@vmware.com>
 <YZYQUn10DrKhSE7L@dhcp22.suse.cz> <Ya89aqij6nMwJrIZ@dhcp22.suse.cz>
 <YbHfBgPQMkjtuHYF@dhcp22.suse.cz> <YbdhdySBaHJ/UxBZ@dhcp22.suse.cz>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <YbdhdySBaHJ/UxBZ@dhcp22.suse.cz>
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On 13.12.21 16:06, Michal Hocko wrote:
> On Thu 09-12-21 11:48:42, Michal Hocko wrote:
> [...]
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 852041f6be41..2d38a431f62f 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1161,19 +1161,21 @@ static void reset_node_present_pages(pg_data_t *pgdat)
>>  }
>>  
>>  /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
>> -static pg_data_t __ref *hotadd_new_pgdat(int nid)
>> +static pg_data_t __ref *hotadd_init_pgdat(int nid)
>>  {
>>  	struct pglist_data *pgdat;
>>  
>>  	pgdat = NODE_DATA(nid);
>> -	if (!pgdat) {
>> -		pgdat = arch_alloc_nodedata(nid);
>> -		if (!pgdat)
>> -			return NULL;
>>  
>> +	/*
>> +	 * NODE_DATA is preallocated (free_area_init) but its internal
>> +	 * state is not allocated completely. Add missing pieces.
>> +	 * Completely offline nodes stay around and they just need
>> +	 * reintialization.
>> +	 */
>> +	if (!pgdat->per_cpu_nodestats) {
>>  		pgdat->per_cpu_nodestats =
>>  			alloc_percpu(struct per_cpu_nodestat);
>> -		arch_refresh_nodedata(nid, pgdat);
> 
> This should really be 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 42211485bcf3..2daa88ce8c80 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1173,7 +1173,7 @@ static pg_data_t __ref *hotadd_init_pgdat(int nid)
>  	 * Completely offline nodes stay around and they just need
>  	 * reintialization.
>  	 */
> -	if (!pgdat->per_cpu_nodestats) {
> +	if (pgdat->per_cpu_nodestats == &boot_nodestats) {
>  		pgdat->per_cpu_nodestats =
>  			alloc_percpu(struct per_cpu_nodestat);
>  	} else {
> 

I'll try giving this some churn later this week -- busy with other stuff.

-- 
Thanks,

David / dhildenb