NFSD: Avoid using rqstp->rq_vers in nfsd_set_fh_dentry()

Currently, fh_verify() makes some daring assumptions about which
version of file handle the caller wants, based on the things it can
find in the passed-in rqstp. The about-to-be-introduced LOCALIO use
case sometimes has no svc_rqst context, so this logic won't work in
that case.

Instead, examine the passed-in file handle. It's .max_size field
should carry information to allow nfsd_set_fh_dentry() to initialize
the file handle appropriately.

The file handle used by lockd and the one created by write_filehandle
never need any of the version-specific fields (which affect things
like write and getattr requests and pre/post attributes).
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

fs/nfsd/nfsfh.c

@@ -267,20 +267,20 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 	fhp->fh_dentry = dentry;
 	fhp->fh_export = exp;
 
-	switch (rqstp->rq_vers) {
-	case 4:
+	switch (fhp->fh_maxsize) {
+	case NFS4_FHSIZE:
 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR)
 			fhp->fh_no_atomic_attr = true;
 		fhp->fh_64bit_cookies = true;
 		break;
-	case 3:
+	case NFS3_FHSIZE:
 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOWCC)
 			fhp->fh_no_wcc = true;
 		fhp->fh_64bit_cookies = true;
 		if (exp->ex_flags & NFSEXP_V4ROOT)
 			goto out;
 		break;
-	case 2:
+	case NFS_FHSIZE:
 		fhp->fh_no_wcc = true;
 		if (EX_WGATHER(exp))
 			fhp->fh_use_wgather = true;