Re: [PATCH] io_uring/net: drop unused 'fast_iov_one' entry

[Dylan Yudaken <dyudaken@gmail.com>]

On Tue, Mar 19, 2024 at 11:37 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> Doesn't really matter at this point, as the fast_iov entries dominate
> the size of io_async_msghdr. But that may not always be the case, so
> drop this unused member. It turns out it got added in a previous commit,
> but never actually used for anything.
>
> Fixes: 9bb66906f23e ("io_uring: support multishot in recvmsg")
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>
> ---
>
> diff --git a/io_uring/net.h b/io_uring/net.h
> index 191009979bcb..9d7962f65f26 100644
> --- a/io_uring/net.h
> +++ b/io_uring/net.h
> @@ -10,7 +10,6 @@ struct io_async_msghdr {
>         union {
>                 struct iovec            fast_iov[UIO_FASTIOV];
>                 struct {
> -                       struct iovec    fast_iov_one;
>                         __kernel_size_t controllen;
>                         int             namelen;
>                         __kernel_size_t payloadlen;
>

I "believe" this is used in the async paths, where fast_iov[0] gets
used (since multishot always has exactly one iovec) and so
fast_iov_one is just a placeholder.
I think that means it's not safe to remove until after your async patches.

Although I haven't verified this by testing.

Dylan