NFSD: Using exp_get for export getting

Don't using cache_get besides export.h, using exp_get for export.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index ec83934..6f5cc76 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -539,8 +539,7 @@
 		       dentry);
 
 	fhp->fh_dentry = dget(dentry); /* our internal copy */
-	fhp->fh_export = exp;
-	cache_get(&exp->h);
+	fhp->fh_export = exp_get(exp);
 
 	if (fhp->fh_handle.fh_version == 0xca) {
 		/* old style filehandle please */