linux-kernel - Re: [PATCH] mm/demotion: Fix kernel error with memory hotplug

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Date:   Thu, 25 Aug 2022 14:16:42 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        linux-mm@...ck.org, akpm@...ux-foundation.org
Cc:     Wei Xu <weixugc@...gle.com>, Huang Ying <ying.huang@...el.com>,
        Yang Shi <shy828301@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Tim C Chen <tim.c.chen@...el.com>,
        Michal Hocko <mhocko@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hesham Almatary <hesham.almatary@...wei.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Alistair Popple <apopple@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Johannes Weiner <hannes@...xchg.org>, jvgediya.oss@...il.com,
        Bharata B Rao <bharata@....com>
Subject: Re: [PATCH] mm/demotion: Fix kernel error with memory hotplug

On 25.08.22 11:20, Aneesh Kumar K.V wrote:
> On memory hot unplug, the kernel removes the node memory type
> from the associated memory tier. Use list_del_init instead of
> list del such that the same memory type can be added back
> to a memory tier on hotplug.
> 
> Without this, we get the below warning and return error on
> adding memory type to a new memory tier.
> 
> [   33.596095] ------------[ cut here ]------------
> [   33.596099] WARNING: CPU: 3 PID: 667 at mm/memory-tiers.c:115 set_node_memory_tier+0xd6/0x2e0
> [   33.596109] Modules linked in: kmem
> 
> ...
> 
> [   33.596126] RIP: 0010:set_node_memory_tier+0xd6/0x2e0
> 
> ....
> [   33.596196]  memtier_hotplug_callback+0x48/0x68
> [   33.596204]  blocking_notifier_call_chain+0x80/0xc0
> [   33.596211]  online_pages+0x25e/0x280
> [   33.596218]  memory_block_change_state+0x176/0x1f0
> [   33.596225]  memory_subsys_online+0x37/0x40
> [   33.596230]  online_store+0x9b/0x130
> [   33.596236]  kernfs_fop_write_iter+0x128/0x1b0
> [   33.596242]  vfs_write+0x24b/0x2c0
> [   33.596249]  ksys_write+0x74/0xe0
> [   33.596254]  do_syscall_64+0x43/0x90
> [   33.596259]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: mm/demotion: Add hotplug callbacks to handle new numa node onlined

Do we have a proper 12-digit commit id as well?

Do we have to cc stable?

> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
> ---
>  mm/memory-tiers.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index a20795bb0e07..ba844fe9cc8c 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -451,7 +451,7 @@ static bool clear_node_memory_tier(int node)
>  		memtype = node_memory_types[node];
>  		node_clear(node, memtype->nodes);
>  		if (nodes_empty(memtype->nodes)) {
> -			list_del(&memtype->tier_sibiling);
> +			list_del_init(&memtype->tier_sibiling);
>  			if (list_empty(&memtier->memory_types))
>  				destroy_memory_tier(memtier);
>  		}


-- 
Thanks,

David / dhildenb