don't bother with ->d_inode->i_sb - it's always equal to ->d_sb

... and neither can ever be NULL

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index c1681ce..a891944 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -426,7 +426,7 @@
 
 static struct super_block *exp_sb(struct svc_export *exp)
 {
-	return d_inode(exp->ex_path.dentry)->i_sb;
+	return exp->ex_path.dentry->d_sb;
 }
 
 static bool fsid_type_ok_for_exp(u8 fsid_type, struct svc_export *exp)