linux-kernel - Re: [RFC][PATCH v4 11/69] lookup_fast(): consolidate the RCU success case

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Message-ID: <CAHk-=wgnpnUy7OiiDbE+Bd=x-K6YyRV_1mvsoP-fhTC2=ez=+A@mail.gmail.com>
Date:   Fri, 13 Mar 2020 17:25:46 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH v4 11/69] lookup_fast(): consolidate the RCU success case

On Fri, Mar 13, 2020 at 4:55 PM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> -                       if (unlikely(negative))
> +                       if (unlikely(!inode))
>                                 return -ENOENT;

Isn't that buggy?

Despite the name, 'inode' isn't an inode pointer. It's a pointer to
the return location.

I think the test should be

        if (unlikely(!*inode))
                return -ENOENT;

and I also suspect that the argument name should be fixed (maybe
"inodepp", maybe something better).

Because the "inode" pointer itself always exists. The callers will
have something like

        struct inode *inode;

and then pass in "&inode" to the function.

And it's possible that I'm talking complete garbage.

               Linus