linux-kernel - Re: [RFC][PATCH v4 15/69] new step_into() flag: WALK

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Message-ID: <CAHk-=widhgJ=hB=dOcQMJzPL9mX+8TdbcAspBXs4FSdiLk2jMw@mail.gmail.com>
Date:   Fri, 13 Mar 2020 17:32:32 -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 15/69] new step_into() flag: WALK_NOFOLLOW

I mentioned this last time (perhaps for a different sequence):

On Fri, Mar 13, 2020 at 4:54 PM Al Viro <viro@...iv.linux.org.uk> wrote:
>
>         if (likely(!d_is_symlink(path->dentry)) ||
> -          !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) {
> +          !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW) ||
> +          flags & WALK_NOFOLLOW) {

Yes, I know that bitwise operations have higher precedence than the
logical ones. And I know & (and &&) have higher precedence than | (and
||).

But I have to _think_ about it every time I see code like this.

I'd really prefer to see

   if ((a & BIT) || (b & ANOTHER_BIT))

over the "equivalent" and shorter

   if (a & BIT || b & ANOTHER_BIT)

Please make it explicit. It wasn't before either, but it _could_ be.

              Linus