Re: [PATCH v5 09/10] io_uring: add support for IORING_OP_LINKAT

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/3/21 6:18 AM, Dmitry Kadashev wrote:
> IORING_OP_LINKAT behaves like linkat(2) and takes the same flags and
> arguments.
> 
> In some internal places 'hardlink' is used instead of 'link' to avoid
> confusion with the SQE links. Name 'link' conflicts with the existing
> 'link' member of io_kiocb.
> 
> Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
> Link: https://lore.kernel.org/io-uring/20210514145259.wtl4xcsp52woi6ab@wittgenstein/
> Signed-off-by: Dmitry Kadashev <dkadashev@gmail.com>
> ---
>  fs/internal.h                 |  2 ++
>  fs/io_uring.c                 | 67 +++++++++++++++++++++++++++++++++++
>  fs/namei.c                    |  2 +-
>  include/uapi/linux/io_uring.h |  2 ++
>  4 files changed, 72 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/internal.h b/fs/internal.h
> index 3b3954214385..15a7d210cc67 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h

[...]
> +
> +static int io_linkat(struct io_kiocb *req, int issue_flags)
> +{
> +	struct io_hardlink *lnk = &req->hardlink;
> +	int ret;
> +
> +	if (issue_flags & IO_URING_F_NONBLOCK)
> +		return -EAGAIN;
> +
> +	ret = do_linkat(lnk->old_dfd, lnk->oldpath, lnk->new_dfd,
> +				lnk->newpath, lnk->flags);

I'm curious, what's difference b/w SYMLINK and just LINK that
one doesn't use old_dfd and another does? Can it be
supported/wished by someone in the future? In that case I'd rather
reserve and verify a field for old_dfd for both, even if one
won't really support it for now.

> +
> +	req->flags &= ~REQ_F_NEED_CLEANUP;
> +	if (ret < 0)
> +		req_set_fail(req);
> +	io_req_complete(req, ret);
> +	return 0;
> +}
> +

-- 
Pavel Begunkov