linux-kernel - Re: [PATCH 2/2] drivers/base/memory: Use array to show memory block state

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Date:   Fri, 20 Jan 2023 14:14:48 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Gavin Shan <gshan@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, david@...hat.com,
        osalvador@...e.de, rafael@...nel.org, shan.gavin@...il.com
Subject: Re: [PATCH 2/2] drivers/base/memory: Use array to show memory block
 state

On Fri, Jan 20, 2023 at 01:57:27PM +0800, Gavin Shan wrote:
> Use an array to show memory block state from '/sys/devices/system/
> memory/memoryX/state', to simplify the code.
> 
> No functional change intended.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  drivers/base/memory.c | 25 ++++++-------------------
>  1 file changed, 6 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index b456ac213610..9474f25c452c 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -141,28 +141,15 @@ static ssize_t state_show(struct device *dev, struct device_attribute *attr,
>  			  char *buf)
>  {
>  	struct memory_block *mem = to_memory_block(dev);
> -	const char *output;
> +	static const char *const mem_state_str[] = {
> +		NULL, "online", "going-offline", NULL, "offline",
> +	};
>  
> -	/*
> -	 * We can probably put these states in a nice little array
> -	 * so that they're not open-coded
> -	 */
> -	switch (mem->state) {
> -	case MEM_ONLINE:
> -		output = "online";
> -		break;
> -	case MEM_OFFLINE:
> -		output = "offline";
> -		break;
> -	case MEM_GOING_OFFLINE:
> -		output = "going-offline";
> -		break;
> -	default:
> -		WARN_ON(1);
> +	if (WARN_ON(mem->state >= ARRAY_SIZE(mem_state_str) ||
> +		    !mem_state_str[mem->state]))

Ick, the whole WARN_ON() should just be removed please.  We don't want
to reboot any systems if this changed incorrectly.

Please fix this up to properly handle this and keep going on, don't mess
with WARN_ON() anymore in code that can recover properly.

thanks,

greg k-h