linux-kernel - Re: [RFC PATCH 2/3] add statmnt(2) syscall

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Message-ID: <20230918-stuhl-spannend-9904d4addc93@brauner>
Date:   Mon, 18 Sep 2023 16:40:43 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Miklos Szeredi <mszeredi@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-man@...r.kernel.org,
        linux-security-module@...r.kernel.org, Karel Zak <kzak@...hat.com>,
        Ian Kent <raven@...maw.net>,
        David Howells <dhowells@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian@...uner.io>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [RFC PATCH 2/3] add statmnt(2) syscall

On Mon, Sep 18, 2023 at 04:32:30PM +0200, Miklos Szeredi wrote:
> On Mon, 18 Sept 2023 at 16:25, Christian Brauner <brauner@...nel.org> wrote:
> 
> > The system call should please have a proper struct like you had in your
> > first proposal. This is what I'm concerned about:
> >
> > int statmount(u64 mnt_id,
> >               struct statmnt __user *st,
> >               size_t size,
> >               unsigned int flags)
> >
> > instead of taking an void pointer.
> 
> So you are not concerned about having ascii strings returned by the
> syscall?   I thought that was the main complaint.

I'm not following. The original proposals were only returning strings
even for basic binary data such as mount flags, propagation options, and
so on and we're using the xattr interface for any type of information.

What we're talking about here is a nicely typed struct which returns two
paths @mnt_root and @mnt_point which can both be represented as u64
pointers with length parameters like we do in other binary structs such
as bpf and clone3 and a few others. That is a compromise I can live
with. I'm really trying to find as much common ground here as we can.