linux-kernel - Re: [PATCH] mm, page_alloc: fix build_zonerefs

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Date:   Thu, 7 Apr 2022 12:06:03 +0200
From:   Juergen Gross <jgross@...e.com>
To:     David Hildenbrand <david@...hat.com>,
        xen-devel@...ts.xenproject.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>, stable@...r.kernel.org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>,
        Michal Hocko <mhocko@...nel.org>,
        Wei Yang <richard.weiyang@...il.com>
Subject: Re: [PATCH] mm, page_alloc: fix build_zonerefs_node()

On 07.04.22 11:46, David Hildenbrand wrote:
> On 07.04.22 11:32, Juergen Gross wrote:
>> Since commit 9d3be21bf9c0 ("mm, page_alloc: simplify zonelist
>> initialization") only zones with free memory are included in a built
>> zonelist. This is problematic when e.g. all memory of a zone has been
>> ballooned out.
>>
>> Use populated_zone() when building a zonelist as it has been done
>> before that commit.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: 9d3be21bf9c0 ("mm, page_alloc: simplify zonelist initialization")
>> Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
>> ---
>>   mm/page_alloc.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index bdc8f60ae462..3d0662af3289 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -6128,7 +6128,7 @@ static int build_zonerefs_node(pg_data_t *pgdat, struct zoneref *zonerefs)
>>   	do {
>>   		zone_type--;
>>   		zone = pgdat->node_zones + zone_type;
>> -		if (managed_zone(zone)) {
>> +		if (populated_zone(zone)) {
>>   			zoneref_set_zone(zone, &zonerefs[nr_zones++]);
>>   			check_highest_zone(zone_type);
>>   		}
> 
> Let's see if we have to find another way to properly handle fadump.

TBH, I don't think this should matter here. A zone can always happen to
have no free memory left, so only handling this case when building the
zonelist can't be the full solution of that problem. It might trigger
a problem more easily, though.

> Acked-by: David Hildenbrand <david@...hat.com>

Thanks,


Juergen


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