linux-kernel - Re: [PATCH v3] mm: fix panic in __alloc

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Date:   Mon, 13 Dec 2021 16:07:18 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...e.com>,
        Alexey Makhalov <amakhalov@...are.com>
Cc:     Dennis Zhou <dennis@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Nico Pache <npache@...hat.com>
Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages

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