[PATCH] objpool: fix minimum alignment of 'struct objpool_slot'

[PATCH] objpool: fix minimum alignment of 'struct objpool_slot'

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.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@arndb.de>
---
 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

Re: [PATCH] objpool: fix minimum alignment of 'struct objpool_slot'

[Yury Norov]

On Tue, Feb 10, 2026 at 11:35:24AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>

Reviewed-by: Yury Norov <ynorov@nvidia.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

Re: [PATCH] objpool: fix minimum alignment of 'struct objpool_slot'

[wuqiang.matt]

On 2026/2/10 18:35, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>
> ---
>   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;
>   

Reviewed-by: wuqiang.matt <wuqiang.matt@bytedance.com>

Regards,
Matt Wu

Re: [PATCH] objpool: fix minimum alignment of 'struct objpool_slot'

[Yury Norov]

Hi Arnd,

Would you like me to route this with my branch? Please let me know if
anything needed on my side.

Thanks,
Yury

On Tue, Feb 10, 2026 at 11:35:24AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>
> ---
>  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