NFSD: Store parent's stat in a separate value

After commit ae7095a7 (nfsd4: helper function for getting mounted_on
ino) we ignore the return value from get_parent_attributes().

Also, the following FATTR4_WORD2_LAYOUT_BLKSIZE uses stat.blksize, so to
avoid overwriting that, use an independent value for the parent's
attributes.
Signed-off-by: NKinglong Mee <kinglongmee@gmail.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4xdr.c

@@ -2675,6 +2675,9 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
 		*p++ = cpu_to_be32(stat.mtime.tv_nsec);
 	}
 	if (bmval1 & FATTR4_WORD1_MOUNTED_ON_FILEID) {
+		struct kstat parent_stat;
+		u64 ino = stat.ino;
+
 		p = xdr_reserve_space(xdr, 8);
 		if (!p)
                 	goto out_resource;
@@ -2683,9 +2686,13 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
 		 * and this is the root of a cross-mounted filesystem.
 		 */
 		if (ignore_crossmnt == 0 &&
-		    dentry == exp->ex_path.mnt->mnt_root)
-			get_parent_attributes(exp, &stat);
-		p = xdr_encode_hyper(p, stat.ino);
+		    dentry == exp->ex_path.mnt->mnt_root) {
+			err = get_parent_attributes(exp, &parent_stat);
+			if (err)
+				goto out_nfserr;
+			ino = parent_stat.ino;
+		}
+		p = xdr_encode_hyper(p, ino);
 	}
 #ifdef CONFIG_NFSD_PNFS
 	if ((bmval1 & FATTR4_WORD1_FS_LAYOUT_TYPES) ||