acl: Realign struct posix_acl to reduce its size by 8 bytes

[PATCH] acl: Realign struct posix_acl to reduce its size by 8 bytes

Posted by Thorsten Blum 1 year, 4 months ago

Reduce posix_acl's struct size by 8 bytes by realigning its members.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 include/linux/posix_acl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index 83b2c5fba1d9..e2d47eb1a7f3 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -28,8 +28,8 @@ struct posix_acl_entry {
 
 struct posix_acl {
 	refcount_t		a_refcount;
-	struct rcu_head		a_rcu;
 	unsigned int		a_count;
+	struct rcu_head		a_rcu;
 	struct posix_acl_entry	a_entries[] __counted_by(a_count);
 };
 
-- 
2.46.2

Re: [PATCH] acl: Realign struct posix_acl to reduce its size by 8 bytes

Posted by Jan Kara 1 year, 4 months ago

On Fri 04-10-24 12:33:57, Thorsten Blum wrote:
> Reduce posix_acl's struct size by 8 bytes by realigning its members.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  include/linux/posix_acl.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
> index 83b2c5fba1d9..e2d47eb1a7f3 100644
> --- a/include/linux/posix_acl.h
> +++ b/include/linux/posix_acl.h
> @@ -28,8 +28,8 @@ struct posix_acl_entry {
>  
>  struct posix_acl {
>  	refcount_t		a_refcount;
> -	struct rcu_head		a_rcu;
>  	unsigned int		a_count;
> +	struct rcu_head		a_rcu;
>  	struct posix_acl_entry	a_entries[] __counted_by(a_count);
>  };
>  
> -- 
> 2.46.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] acl: Realign struct posix_acl to reduce its size by 8 bytes

Posted by Thorsten Blum 1 year, 4 months ago

On 4. Oct 2024, at 15:37, Jan Kara wrote:
> On Fri 04-10-24 12:33:57, Thorsten Blum wrote:
>> Reduce posix_acl's struct size by 8 bytes by realigning its members.
>> 
>> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> 
> Looks good. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>

We should probably add:

Fixes: b0ab04a8ffd8 ("acl: Annotate struct posix_acl with __counted_by()")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202409260949.a1254989-oliver.sang@intel.com

as this patch is also a workaround for a Clang __bdos() bug (see the
Closes: link for details).

Thanks,
Thorsten

Re: [PATCH] acl: Realign struct posix_acl to reduce its size by 8 bytes

Posted by Thorsten Blum 1 year, 4 months ago

On 4. Oct 2024, at 22:11, Thorsten Blum wrote:
> On 4. Oct 2024, at 15:37, Jan Kara wrote:
>> On Fri 04-10-24 12:33:57, Thorsten Blum wrote:
>>> Reduce posix_acl's struct size by 8 bytes by realigning its members.
>>> 
>>> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
>> 
>> Looks good. Feel free to add:
>> 
>> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> We should probably add:
> 
> Fixes: b0ab04a8ffd8 ("acl: Annotate struct posix_acl with __counted_by()")
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202409260949.a1254989-oliver.sang@intel.com

Just realized Christian dropped b0ab04a8ffd8 (although it's still in
linux-next). I guess we don't need these tags then.

> as this patch is also a workaround for a Clang __bdos() bug (see the
> Closes: link for details).
> 
> Thanks,
> Thorsten