linux-kernel - Re: [PATCH v2 30/36] fs: add do_linkat() helper and ksys_link() wrapper; remove in-kernel calls to syscall

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Message-ID: <20180317171129.GD3351@light.dominikbrodowski.net>
Date:   Sat, 17 Mar 2018 18:11:29 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 30/36] fs: add do_linkat() helper and ksys_link()
 wrapper; remove in-kernel calls to syscall

On Thu, Mar 15, 2018 at 09:30:58PM +0100, Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 8:05 PM, Dominik Brodowski
> <linux@...inikbrodowski.net> wrote:
> >
> >   */
> > -SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
> > -               int, newdfd, const char __user *, newname, int, flags)
> > +int do_linkat(int olddfd, const char __user *oldname, int newdfd,
> > +             const char __user *newname, int flags)
> >  {
> >         struct dentry *new_dentry;
> >         struct path old_path, new_path;
> 
> For consistency with other do_*() functions, I think it would be nice
> to make this one not take a __user pointer either. However, I
> have no idea how to do that without making the common case worse.
> 
> > --- a/init/initramfs.c
> > +++ b/init/initramfs.c
> > @@ -306,7 +306,7 @@ static int __init maybe_link(void)
> >         if (nlink >= 2) {
> >                 char *old = find_link(major, minor, ino, mode, collected);
> >                 if (old)
> > -                       return (sys_link(old, collected) < 0) ? -1 : 1;
> > +                       return (ksys_link(old, collected) < 0) ? -1 : 1;
> >         }
> >         return 0;
> >  }
> 
> Since this is the only caller outside of fs/namei.c, maybe it can be
> changed to use vfs_link() instead? That might still be a larger rework
> than you want to do.

In line with what I propose generally for this series, I have added the
following paragraph to the commit message:

	In the near future, the only fs-external user of ksys_link() should be
	converted to use vfs_link() instead.

Thanks,
	Dominik