Re: [PATCH v2 3/3] hpsa: add an assert to prevent from __packed reintroduction

[Arnd Bergmann <arnd@xxxxxxxxxx>]

On Tue, Mar 30, 2021 at 9:23 AM Sergei Trofimovich <slyfox@xxxxxxxxxx> wrote:

> +/*
> + * Make sure our embedded atomic variable is aligned. Otherwise we break atomic
> + * operations on architectures that don't support unaligned atomics like IA64.
> + *
> + * The assert guards against reintroductin against unwanted __packed to
> + * the struct CommandList.
> + */
> +static_assert(offsetof(struct CommandList, refcount) % __alignof__(atomic_t) == 0);
> +

There are a few other members that need to be aligned: the work_struct
has another
atomic_t inside it, and there are a few pointers that might rely on
being written to
atomically.

While you could add a static_assert for each member, the easier solution is to
just not ask for the members to be misaligned in the first place.

       Arnd