linux-kernel - Re: [PATCH 00/29] fs: require filesystems to explicitly opt-in to nfsd export support

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Message-id: <176877859306.16766.15009835437490907207@noble.neil.brown.name>
Date: Mon, 19 Jan 2026 10:23:13 +1100
From: NeilBrown <neilb@...mail.net>
To: "Jeff Layton" <jlayton@...nel.org>
Cc: "Amir Goldstein" <amir73il@...il.com>,
 "Christian Brauner" <brauner@...nel.org>,
 "Alexander Viro" <viro@...iv.linux.org.uk>,
 "Chuck Lever" <chuck.lever@...cle.com>,
 "Olga Kornievskaia" <okorniev@...hat.com>,
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Subject: Re: [PATCH 00/29] fs: require filesystems to explicitly opt-in to
 nfsd export support

On Fri, 16 Jan 2026, Jeff Layton wrote:
> On Thu, 2026-01-15 at 19:17 +0100, Amir Goldstein wrote:
> > On Thu, Jan 15, 2026 at 6:48 PM Jeff Layton <jlayton@...nel.org> wrote:
> > > 
> > > In recent years, a number of filesystems that can't present stable
> > > filehandles have grown struct export_operations. They've mostly done
> > > this for local use-cases (enabling open_by_handle_at() and the like).
> > > Unfortunately, having export_operations is generally sufficient to make
> > > a filesystem be considered exportable via nfsd, but that requires that
> > > the server present stable filehandles.
> > 
> > Where does the term "stable file handles" come from? and what does it mean?
> > Why not "persistent handles", which is described in NFS and SMB specs?
> > 
> > Not to mention that EXPORT_OP_PERSISTENT_HANDLES was Acked
> > by both Christoph and Christian:
> > 
> > https://lore.kernel.org/linux-fsdevel/20260115-rundgang-leihgabe-12018e93c00c@brauner/
> > 
> > Am I missing anything?
> > 
> 
> This was Chuck's suggested name. His point was that STABLE means that
> the FH's don't change during the lifetime of the file.
> 
> I don't much care about the flag name, so if everyone likes PERSISTENT
> better I'll roll with that.

I don't like PERSISTENT.
I'd rather call a spade a spade.

  EXPORT_OP_SUPPORTS_NFS_EXPORT
or
  EXPORT_OP_NOT_NFS_COMPATIBLE

The issue here is NFS export and indirection doesn't bring any benefits.

NeilBrown


> 
> Also, on the ovl patch: will fix...
> 
> Thanks for the review!
> -- 
> Jeff Layton <jlayton@...nel.org>
>