linux-kernel - Re: [PATCH] drivers/base/node: Handle error properly in register_one

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Message-ID: <aGUqQbybFXd6uJu-@localhost.localdomain>
Date: Wed, 2 Jul 2025 14:46:57 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Donet Tom <donettom@...ux.ibm.com>
Cc: David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, Zi Yan <ziy@...dia.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ritesh Harjani <ritesh.list@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Alison Schofield <alison.schofield@...el.com>,
	Yury Norov <yury.norov@...il.com>,
	Dave Jiang <dave.jiang@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] drivers/base/node: Handle error properly in
 register_one_node()

On Wed, Jul 02, 2025 at 06:28:56AM -0500, Donet Tom wrote:
> If register_node() returns an error, it is not handled correctly.
> The function will proceed further and try to register CPUs under the
> node, which is not correct.
> 
> So, in this patch, if register_node() returns an error, we return
> immediately from the function.
> 
> Signed-off-by: Donet Tom <donettom@...ux.ibm.com>
> ---
> 
... 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index bef84f01712f..aec991b4c0b2 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -885,6 +885,8 @@ int register_one_node(int nid)
>  	node_devices[nid] = node;
>  
>  	error = register_node(node_devices[nid], nid);
> +	if (error)
> +		return error;

Ok, all current callers (based on mm-unstable) panic or BUG() if this fails,
but powerpc, in init_phb_dynamic(), which keeps on going.
Unless it panics somewhere down the road as well.

So I think we need to: 

 node_devices[nid] = NULL
 kfree(node)

 ?

Also, once Hannes fix lands, we might need that as well.

Anyway, I'd suggest you hold on until Hannes fix lands, so we can later
rebase all your mem-hotplug on top of that [1].

[1] https://lore.kernel.org/linux-mm/86f89a65-f0f6-4462-9eea-ac691de2f3b6@suse.de/T/#mbf392eb390b8053f96be50da3b40dfd9b62dd389


-- 
Oscar Salvador
SUSE Labs