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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 10 Dec 2020 10:55:58 -0800
Message-ID: <CAHk-=wicKF87YsiQpdK0B26Mk3UhRNrBEcOv7h=ohFKLjRM4DQ@mail.gmail.com>
Subject: Re: namei.c LOOKUP_NONBLOCK (was "Re: [GIT PULL] io_uring fixes for 5.10-rc")
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Al Viro <viro@zeniv.linux.org.uk>,
        io-uring <io-uring@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Thu, Dec 10, 2020 at 9:32 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> Here's a potentially better attempt - basically we allow LOOKUP_NONBLOCK
> with LOOKUP_RCU, and if we end up dropping LOOKUP_RCU, then we generally
> return -EAGAIN if LOOKUP_NONBLOCK is set as we can no longer guarantee
> that we won't block.

Looks sane to me.

I don't love the "__unlazy_walk vs unlazy_walk" naming - I think it
needs to be more clear about what the difference is, but I think the
basic patch looks sane, and looks about as big as I would have
expected it to be.

But yes, I'll leave it to Al.

And if we do this - and I think we should - I'd also love to see a new
flag in 'struct open_how' to openat2(), even if it's only to enable
tests. RESOLVE_NONBLOCK?

               Linus