On Fri, Jan 16, 2026 at 1:36 PM Jeff Layton <[email protected]> wrote: > > On Thu, 2026-01-15 at 20:23 +0100, Amir Goldstein wrote: > > On Thu, Jan 15, 2026 at 6:51 PM Jeff Layton <[email protected]> wrote: > > > > > > Some filesystems have grown export operations in order to provide > > > filehandles for local usage. Some of these filesystems are unsuitable > > > for use with nfsd, since their filehandles are not persistent across > > > reboots. > > > > > > In __fh_verify, check whether EXPORT_OP_STABLE_HANDLES is set > > > and return nfserr_stale if it isn't. > > > > > > Signed-off-by: Jeff Layton <[email protected]> > > > --- > > > fs/nfsd/nfsfh.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c > > > index > > > ed85dd43da18e6d4c4667ff14dc035f2eacff1d6..da9d5fb2e6613c2707195da2e8678b3fcb3d444d > > > 100644 > > > --- a/fs/nfsd/nfsfh.c > > > +++ b/fs/nfsd/nfsfh.c > > > @@ -334,6 +334,10 @@ __fh_verify(struct svc_rqst *rqstp, > > > dentry = fhp->fh_dentry; > > > exp = fhp->fh_export; > > > > > > + error = nfserr_stale; > > > + if (!(dentry->d_sb->s_export_op->flags & > > > EXPORT_OP_STABLE_HANDLES)) > > > + goto out; > > > + > > > trace_nfsd_fh_verify(rqstp, fhp, type, access); > > > > > > > IDGI. Don't you want to deny the export of those fs in check_export()? > > By the same logic that check_export() checks for can_decode_fh() > > not for can_encode_fh(). > > > > It certainly won't hurt to add a check for this to check_export(), and > I've gone ahead and done so. To be clear, doing that won't prevent the > filesystem from being exported, but you will get a warning like this > when you try: > > exportfs: /sys/fs/cgroup does not support NFS export > > That export will still show up in mountd though, so this is just a > warning. Trying to mount it though will fail. >
Oh, I did not know. What an odd user experience. Anyway, better than no warning at all. Thanks, Amir.
