On 2022/06/02 16:38, Arnd Bergmann wrote:
>> But let's cc the tomoyo and chelsio people.
>
> I think both of them work because the structures are always
> embedded inside of larger structures that have at least word
> alignment. This is the thing I was looking for, and the
> __packed attribute was added in error, most likely copied
> from somewhere else.
The __packed in "struct tomoyo_shared_acl_head" is to embed next
naturally-aligned member of a larger struct into the bytes that
would have been wasted if __packed is not specified. For example,
struct tomoyo_shared_acl_head {
struct list_head list;
atomic_t users;
} __packed;
struct tomoyo_condition {
struct tomoyo_shared_acl_head head;
u32 size; /* Memory size allocated for this entry. */
(...snipped...)
};
saves 4 bytes on 64 bits build.
If the next naturally-aligned member of a larger struct is larger than
the bytes that was saved by __packed, the saved bytes will be unused.
