linux-kernel - Re: [PATCH 2/3 v4] devpts: resolve devpts bind-mounts

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Date:   Mon, 12 Mar 2018 17:37:14 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 2/3 v4] devpts: resolve devpts bind-mounts

On Mon, Mar 12, 2018 at 5:01 PM, Christian Brauner
<christian.brauner@...ntu.com> wrote:
>
> ChangeLog v3->v4:
> * simplify if condition

Ok, I definitely prefer this simpler version.

We could simplify it even more, though. That end could be just

        ...
        dput(path.dentry);
        if (!err) {
                if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
                        return path.mnt;
                err = -ENODEV;
        }

        mntput(path.mnt);
        return ERR_PTR(err);

instead.

And it might be worth adding a comment that devpts_ptmx_path() always
returns a DEVPTS filesystem of an error. I already wrote out "that's
not right, you can't do DEVPTS_SB() without checking s_magic", but
devpts_ptmx_path() will have done that already.

             Linus