Re: Support for shutdown

[Norman Maurer <norman.maurer@googlemail.com>]

Yes in 5.8 branch would be the easiest...

You rock!

Bye
Norman

> Am 05.09.2020 um 19:11 schrieb Jens Axboe <axboe@kernel.dk>:
> 
> On 9/5/20 11:03 AM, Norman Maurer wrote:
>> Hi there,
>> 
>> As you may have noticed from previous emails we are currently writing
>> a new transport for netty that will use io_uring under the hood for
>> max performance. One thing that is missing at the moment is the
>> support for “shutdown”. Shutdown is quite useful in TCP land when you
>> only want to close either input or output of the connection.
>> 
>> Is this something you think that can be added in the future ? This
>> would be a perfect addition to the already existing close support.
> 
> Something like this should do it, should just be split into having the
> net part as a prep patch. I can add this to the 5.8 branch if that's
> easier for you to test?
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index a9a625ceea5f..67714078e85d 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -529,6 +529,11 @@ struct io_statx {
>    struct statx __user        *buffer;
> };
> 
> +struct io_shutdown {
> +    struct file            *file;
> +    int                how;
> +};
> +
> struct io_completion {
>    struct file            *file;
>    struct list_head        list;
> @@ -666,6 +671,7 @@ struct io_kiocb {
>        struct io_splice    splice;
>        struct io_provide_buf    pbuf;
>        struct io_statx        statx;
> +        struct io_shutdown    shutdown;
>        /* use only after cleaning per-op data, see io_clean_op() */
>        struct io_completion    compl;
>    };
> @@ -922,6 +928,9 @@ static const struct io_op_def io_op_defs[] __read_mostly = {
>        .hash_reg_file        = 1,
>        .unbound_nonreg_file    = 1,
>    },
> +    [IORING_OP_SHUTDOWN] = {
> +        .needs_file        = 1,
> +    },
> };
> 
> enum io_mem_account {
> @@ -3367,6 +3376,44 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
>    return ret;
> }
> 
> +static int io_shutdown_prep(struct io_kiocb *req,
> +                const struct io_uring_sqe *sqe)
> +{
> +#if defined(CONFIG_NET)
> +    if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL|IORING_SETUP_SQPOLL)))
> +        return -EINVAL;
> +    if (sqe->ioprio || sqe->off || sqe->addr || sqe->len ||
> +        sqe->rw_flags || sqe->buf_index)
> +        return -EINVAL;
> +
> +    req->shutdown.how = READ_ONCE(sqe->len);
> +    return 0;
> +#else
> +    return -EOPNOTSUPP;
> +#endif
> +}
> +
> +static int io_shutdown(struct io_kiocb *req, bool force_nonblock)
> +{
> +#if defined(CONFIG_NET)
> +    struct socket *sock;
> +    int ret;
> +
> +    if (force_nonblock)
> +        return -EAGAIN;
> +
> +    sock = sock_from_file(req->file, &ret);
> +    if (unlikely(!sock))
> +        return ret;
> +
> +    ret = __sys_shutdown_sock(sock, req->shutdown.how);
> +    io_req_complete(req, ret);
> +    return 0;
> +#else
> +    return -EOPNOTSUPP;
> +#endif
> +}
> +
> static int __io_splice_prep(struct io_kiocb *req,
>                const struct io_uring_sqe *sqe)
> {
> @@ -5588,6 +5635,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
>    case IORING_OP_TEE:
>        ret = io_tee_prep(req, sqe);
>        break;
> +    case IORING_OP_SHUTDOWN:
> +        ret = io_shutdown_prep(req, sqe);
> +        break;
>    default:
>        printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
>                req->opcode);
> @@ -5942,6 +5992,14 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
>        }
>        ret = io_tee(req, force_nonblock);
>        break;
> +    case IORING_OP_SHUTDOWN:
> +        if (req) {
> +            ret = io_shutdown_prep(req, sqe);
> +            if (ret < 0)
> +                break;
> +        }
> +        ret = io_shutdown(req, force_nonblock);
> +        break;
>    default:
>        ret = -EINVAL;
>        break;
> diff --git a/include/linux/socket.h b/include/linux/socket.h
> index e9cb30d8cbfb..385894b4a8bb 100644
> --- a/include/linux/socket.h
> +++ b/include/linux/socket.h
> @@ -436,6 +436,7 @@ extern int __sys_getpeername(int fd, struct sockaddr __user *usockaddr,
>                 int __user *usockaddr_len);
> extern int __sys_socketpair(int family, int type, int protocol,
>                int __user *usockvec);
> +extern int __sys_shutdown_sock(struct socket *sock, int how);
> extern int __sys_shutdown(int fd, int how);
> 
> extern struct ns_common *get_net_ns(struct ns_common *ns);
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 7539d912690b..2301c37e86cb 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -132,6 +132,7 @@ enum {
>    IORING_OP_PROVIDE_BUFFERS,
>    IORING_OP_REMOVE_BUFFERS,
>    IORING_OP_TEE,
> +    IORING_OP_SHUTDOWN,
> 
>    /* this goes last, obviously */
>    IORING_OP_LAST,
> diff --git a/net/socket.c b/net/socket.c
> index 0c0144604f81..8616962c27bc 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2192,6 +2192,17 @@ SYSCALL_DEFINE5(getsockopt, int, fd, int, level, int, optname,
>  *    Shutdown a socket.
>  */
> 
> +int __sys_shutdown_sock(struct socket *sock, int how)
> +{
> +    int err;
> +
> +    err = security_socket_shutdown(sock, how);
> +    if (!err)
> +        err = sock->ops->shutdown(sock, how);
> +
> +    return err;
> +}
> +
> int __sys_shutdown(int fd, int how)
> {
>    int err, fput_needed;
> @@ -2199,9 +2210,7 @@ int __sys_shutdown(int fd, int how)
> 
>    sock = sockfd_lookup_light(fd, &err, &fput_needed);
>    if (sock != NULL) {
> -        err = security_socket_shutdown(sock, how);
> -        if (!err)
> -            err = sock->ops->shutdown(sock, how);
> +        err = __sys_shutdown_sock(sock, how);
>        fput_light(sock->file, fput_needed);
>    }
>    return err;
> 
> -- 
> Jens Axboe
>