Message-ID: <24b4455c-aff9-ca9f-e29f-350833e7a0d1@virtuozzo.com>
Date:   Mon, 6 Dec 2021 16:19:12 +0300
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Subject: Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker_info on
 offlined nodes
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To:     David Hildenbrand <david@redhat.com>,
        Michal Hocko <mhocko@suse.com>, Nico Pache <npache@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, shakeelb@google.com,
        shy828301@gmail.com, guro@fb.com, vbabka@suse.cz,
        vdavydov.dev@gmail.com, raquini@redhat.com
References: <20211206033338.743270-1-npache@redhat.com>
 <20211206033338.743270-3-npache@redhat.com> <Ya3WcYKcej8XEI0W@dhcp22.suse.cz>
 <d9d14beb-ee20-7ebb-e007-fbf58fb28535@redhat.com>
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
In-Reply-To: <d9d14beb-ee20-7ebb-e007-fbf58fb28535@redhat.com>
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On 06.12.2021 13:45, David Hildenbrand wrote:
>> This doesn't seen complete. Slab shrinkers are used in the reclaim
>> context. Previously offline nodes could be onlined later and this would
>> lead to NULL ptr because there is no hook to allocate new shrinker
>> infos. This would be also really impractical because this would have to
>> update all existing memcgs...
> 
> Instead of going through the trouble of updating...
> 
> ...  maybe just keep for_each_node() and check if the target node is
> offline. If it's offline, just allocate from the first online node.
> After all, we're not using __GFP_THISNODE, so there are no guarantees
> either way ...

Hm, can't we add shrinker maps allocation to __try_online_node() in addition
to this patch?