NFSD: Put exports after nfsd4_layout_verify fail

Fix commit 9cf514cc (nfsd: implement pNFS operations).
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -1237,8 +1237,8 @@ nfsd4_getdeviceinfo(struct svc_rqst *rqstp,
 		nfserr = ops->proc_getdeviceinfo(exp->ex_path.mnt->mnt_sb, gdp);
 
 	gdp->gd_notify_types &= ops->notify_types;
-	exp_put(exp);
 out:
+	exp_put(exp);
 	return nfserr;
 }