Re: RFC: checking file systems support UF_HIDDEN, UF_SYSTEM

On Wed, Jul 2, 2025, 3:03 PM Rick Macklem <rick.macklem@gmail.com> wrote:

> Hi,
>
> I am implementing the "hidden" and "system" attributes for
> NFSv4 using UF_HIDDEN and UF_SYSTEM.
>
> In a couple of places in the code, I need to know if a file
> system supports these flags.
> I can think of two ways to do this.
> #1 - Create a new VFCF_HIDSYS flag that is set via VFS_SET()
>        for file systems that support the UF_HIDDEN and UF_SYSTEM
>        flags and test for that flag being set.
> or
> #2 - Write it this way...
>       if (strcmp(vp->v_mount->mnt_vfc->vfc_name, "zfs") != 0 ||
>           strcmp(vp->v_mount->mnt_vfc->vfc_name, "ufs") != 0 ||
>           strcmp(vp->v_mount->mnt_vfc->vfc_name, "msdosfs") != 0 ||
>           strcmp(vp->v_mount->mnt_vfc->vfc_name, "tmpfs") != 0)
>
> Which do you think is preferable (or do you have another idea)?
>
> Thanks for any comments, rick
>

The strcmp method isn't very good, because it doesn't account for the
possibility that some filesystems may only support the flags conditionally,
depending on formatting options. I vote for method 1.

>