Re: RFC: Marking file system va_filerev style

On Wed, Jan 08, 2025 at 04:39:36PM -0800, Rick Macklem wrote:
> Hi,
> 
> Back in Sept. Richard reported a problem with a
> FreeBSD server serving NFSv4 to Linux clients,
> where the file attributes would get messed up
> sometimes. (I can't recall if he posted me or a mailing
> list.)
> 
> Anyhow, He tried a patch I gave him that told the
> Linux client that the Change attribute (va_filerev)
> increments for each change.
> --> This appears to have fixed the problem.
> 
> However, this patch should really report what the
> exported fs does w.r.t. va_filerev and not just guess
> that it increments it.
> 
> So, the question is, how do I have file systems report
> how they generate va_filerev?
> My current thought is a new MNTK_xxx flag set by
> the filesystem in its mount point to indicate it increments
> it upon each change (which is what UFS and ZFS currently
> does, I think?)
> 
> Does this sound reasonable?

Is this a per-mount property, or a generic filesystem-type property (for
me, the nature of the indicated feature tends to mean per-type).  Then
it might be that a VFCF_ flag is the more natural solution than MNTK_ one.