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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Date:   Thu, 15 Mar 2018 21:30:58 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Dominik Brodowski <linux@...inikbrodowski.net>
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 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.

        Arnd