Re: [PATCH 1/5] eventpoll: Convert epoll_put_uevent() to scoped user access

[Christophe Leroy (CS GROUP)]

Le 10/03/2026 à 08:54, renpanpan a écrit :
> [Vous ne recevez pas souvent de courriers de renpanpan@xxxxxxxxxx. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
>
> From: Eric Dumazet <edumazet@xxxxxxxxxx>
>
> Saves two function calls, and one stac/clac pair.
>
> stac/clac is rather expensive on older cpus like Zen 2.
>
> A synthetic network stress test gives a ~1.5% increase of pps
> on AMD Zen 2.
>
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---
>   include/linux/eventpoll.h | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> index ccb478eb174b..ea9ca0e4172a 100644
> --- a/include/linux/eventpoll.h
> +++ b/include/linux/eventpoll.h
> @@ -82,11 +82,14 @@ static inline struct epoll_event __user *
>   epoll_put_uevent(__poll_t revents, __u64 data,
>                   struct epoll_event __user *uevent)
>   {
> -       if (__put_user(revents, &uevent->events) ||
> -           __put_user(data, &uevent->data))
> -               return NULL;
> -
> +       scoped_user_write_access_size(uevent, sizeof(*uevent), efault) {

As already mentionned this could be simplified:

	scoped_user_write_access(uevent, efault) {

> +               unsafe_put_user(revents, &uevent->events, efault);
> +               unsafe_put_user(data, &uevent->data, efault);
> +       }
>          return uevent+1;
> +
> +efault:
> +       return NULL;
>   }
>   #endif
>
> --
> 2.25.1