Re: [PATCH] io_uring: Add IORING_OP_DUP

[Daniele Di Proietto <daniele.di.proietto@gmail.com>]

On Tue, Mar 10, 2026 at 4:14 PM Keith Busch <kbusch@kernel.org> wrote:
>
> On Tue, Mar 10, 2026 at 03:49:33PM +0000, Daniele Di Proietto wrote:
> > +int io_dup(struct io_kiocb *req, unsigned int issue_flags)
> > +{
> > +     struct io_dup *id;
> > +     int ret;
> > +
> > +     id = io_kiocb_to_cmd(req, struct io_dup);
> > +     ret = replace_fd(id->new_fd, id->file, id->o_flags);
>
> It looks like there are a few conditions where replace_fd may block,
> so it may be a problem to call it from the uring enter context since it
> will block progress through the sq ring for subsequent commands.

You're right, thanks!

I can punt the request to io-wq if the file to be closed has a
->flush() method, as asked by Jens.

Any other conditions you're worried about? expand_files() might block
if another thread is trying to expand the file table concurrently, but
io_install_fixed_fd() has the same problem, right?