ceph: avoid updating directory inode's i_size accidentally

Directory inode's i_size is used by readdir cache.
Signed-off-by: Yan, Zheng <zyan@redhat.com>

fs/ceph/inode.c

@@ -549,6 +549,10 @@ int ceph_fill_file_size(struct inode *inode, int issued,
 	if (ceph_seq_cmp(truncate_seq, ci->i_truncate_seq) > 0 ||
 	    (truncate_seq == ci->i_truncate_seq && size > inode->i_size)) {
 		dout("size %lld -> %llu\n", inode->i_size, size);
+		if (size > 0 && S_ISDIR(inode->i_mode)) {
+			pr_err("fill_file_size non-zero size for directory\n");
+			size = 0;
+		}
 		i_size_write(inode, size);
 		inode->i_blocks = (size + (1<<9) - 1) >> 9;
 		ci->i_reported_size = size;