linux-kernel - Re: [PATCH] objpool: fix minimum alignment of 'struct objpool

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Message-ID: <aYzviPrD8A7n8KcB@yury>
Date: Wed, 11 Feb 2026 16:07:20 -0500
From: Yury Norov <ynorov@...dia.com>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Matt Wu <wuqiang.matt@...edance.com>, Arnd Bergmann <arnd@...db.de>,
	Yury Norov <yury.norov@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] objpool: fix minimum alignment of 'struct objpool_slot'

On Tue, Feb 10, 2026 at 11:35:24AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Members of objpool_slot get passed into try_cmpxchg_release(),
> which does not work on most architectures unless they are
> naturally aligned. Marking the structure as packed makes it
> only byte-aligned, as shown by this (normally disabled) warning:
> 
> include/linux/objpool.h:156:56: warning: taking address of packed member of 'struct objpool_slot' may result in an unaligned pointer value [-Waddress-of-packed-member]
>   156 |                 if (try_cmpxchg_release(&slot->head, &head, head + 1))
>       |                                                       ~^~~~~~~~~~~~
> 
> As the struct members are all tightly packed on all architectures,
> Just remove the '__packed annotation to give it the required
> alignment of the native word size.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Yury Norov <ynorov@...dia.com>

> ---
>  include/linux/objpool.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/objpool.h b/include/linux/objpool.h
> index b713a1fe7521..f678b35b20b1 100644
> --- a/include/linux/objpool.h
> +++ b/include/linux/objpool.h
> @@ -56,7 +56,7 @@ struct objpool_slot {
>  	uint32_t            last;
>  	uint32_t            mask;
>  	void               *entries[];
> -} __packed;
> +};
>  
>  struct objpool_head;
>  
> -- 
> 2.39.5