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From: Dmitry Kadashev <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: Jens Axboe <[email protected]>,
	Alexander Viro <[email protected]>,
	Christian Brauner <[email protected]>,
	[email protected],
	io-uring <[email protected]>
Subject: Re: [PATCH v5 09/10] io_uring: add support for IORING_OP_LINKAT
Date: Wed, 23 Jun 2021 13:09:36 +0700	[thread overview]
Message-ID: <CAOKbgA71puEF4Te+svaRD1MRYEpkQOLigq5xQu85Ch4rDO7_Rw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>

On Tue, Jun 22, 2021 at 6:48 PM Pavel Begunkov <[email protected]> wrote:
>
> 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 <[email protected]>
> > Link: https://lore.kernel.org/io-uring/20210514145259.wtl4xcsp52woi6ab@wittgenstein/
> > Signed-off-by: Dmitry Kadashev <[email protected]>
> > ---
> >  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?

Symlink's content does not have to exist, it's pretty much an arbitrary string.
E.g. try `ln -s http://example.com/ foo` :)

> Can it be supported/wished by someone in the future?

I don't really know. I guess it could be imagined that someone wants to try and
resolve the full target name against some dfd. But to me the whole idea looks
inherently problematic. Accepting the old dfd feels like the path is going to
be resolved, and historically it is not the case, and we'd need a special dfd
value to mean "do not resolve", and AT_FDCWD won't work for this (since it
means "resolve against the CWD", not "do not resolve").

> 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.

If I understand you correctly, at this point you mean just checking that
old_dfd is not set (i.e. == -1)? I'll add a check.

-- 
Dmitry Kadashev

  reply	other threads:[~2021-06-23  6:09 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03  5:18 [PATCH v5 00/10] io_uring: add mkdir, [sym]linkat and mknodat support Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 01/10] fs: make do_mkdirat() take struct filename Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 02/10] io_uring: add support for IORING_OP_MKDIRAT Dmitry Kadashev
2021-06-22 11:41   ` Pavel Begunkov
2021-06-22 11:50     ` Pavel Begunkov
2021-06-23  6:41       ` Dmitry Kadashev
2021-06-23 11:53         ` Pavel Begunkov
2021-06-24 11:11           ` Dmitry Kadashev
2021-06-24 12:21             ` Pavel Begunkov
2021-06-28  8:17               ` Dmitry Kadashev
2021-07-07 14:06                 ` Pavel Begunkov
2021-07-12 12:44                   ` Dmitry Kadashev
2021-07-12 13:14                     ` Pavel Begunkov
2021-06-22 17:41   ` Pavel Begunkov
2021-06-23  0:41     ` Jens Axboe
2021-06-23  5:50     ` Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 03/10] fs: make do_mknodat() take struct filename Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 04/10] fs: make do_symlinkat() " Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 05/10] namei: add getname_uflags() Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 06/10] fs: make do_linkat() take struct filename Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 07/10] fs: update do_*() helpers to return ints Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 08/10] io_uring: add support for IORING_OP_SYMLINKAT Dmitry Kadashev
2021-06-22 11:36   ` Pavel Begunkov
2021-06-23  5:45     ` Dmitry Kadashev
2021-06-03  5:18 ` [PATCH v5 09/10] io_uring: add support for IORING_OP_LINKAT Dmitry Kadashev
2021-06-22 11:48   ` Pavel Begunkov
2021-06-23  6:09     ` Dmitry Kadashev [this message]
2021-06-23 13:13       ` Pavel Begunkov
2021-06-03  5:18 ` [PATCH v5 10/10] io_uring: add support for IORING_OP_MKNODAT Dmitry Kadashev
2021-06-22 11:52   ` Pavel Begunkov
2021-06-23  6:26     ` Dmitry Kadashev
2021-06-23 11:58       ` Pavel Begunkov
2021-06-24  2:36       ` Jens Axboe
2021-06-18  6:24 ` [PATCH v5 00/10] io_uring: add mkdir, [sym]linkat and mknodat support Dmitry Kadashev
2021-06-18 16:10   ` Jens Axboe
2021-06-21 15:21     ` Jens Axboe
2021-06-22  8:12       ` Christian Brauner
2021-06-22  8:34         ` Dmitry Kadashev
2021-06-29 13:06           ` Christian Brauner
2021-06-22 17:26         ` Jens Axboe
2021-06-22  8:26       ` Dmitry Kadashev
2021-06-21 15:57 ` Jens Axboe
2021-06-21 15:59   ` Jens Axboe
2021-06-22 11:56 ` Pavel Begunkov
2021-06-22 17:26   ` Jens Axboe
2021-06-22 17:28     ` Pavel Begunkov
2021-06-22 17:32       ` Jens Axboe
2021-06-23  5:37         ` Dmitry Kadashev
2021-06-23  5:49         ` Dmitry Kadashev
2021-06-24  2:37           ` Jens Axboe
2021-06-24 10:55             ` Dmitry Kadashev
2021-06-23  5:35   ` Dmitry Kadashev
2021-06-24  2:37     ` Jens Axboe

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