Disable inplace update link change entry

There is a crash consistency issue with link after rename.
nova_rename() will append a link change entry to the log. nova_link()
after that, will modify the existing link change entry instead of
appending a new one, because there is no snapshot taken. So, a crash
after nova_append_link_change_entry() will update the link change entry's
links to 2.

Currently disable inplace update link change entry as a workaround.

Author: Andiry

fs/nova/log.c

@@ -707,6 +707,14 @@ int nova_invalidate_link_change_entry(struct super_block *sb,
 static int nova_can_inplace_update_lcentry(struct super_block *sb,
 	struct nova_inode_info_header *sih, u64 epoch_id)
 {
+	/* FIXME: There is a crash consistency issue with link after rename.
+	 * rename will create a link change entry to the log. nova_link() after
+	 * that will inplace update the link change entry. A crash after
+	 * nova_append_link_change_entry() in nova_link() will leave the inode
+	 * in inconsistent state (number of links) in this case.
+	 * Currently, disable inplace update link change entry.
+	 */
+# if 0
 	u64 last_log = 0;
 	struct nova_link_change_entry *entry = NULL;
 
@@ -717,7 +725,7 @@ static int nova_can_inplace_update_lcentry(struct super_block *sb,
 		if (entry->epoch_id == epoch_id)
 			return 1;
 	}
-
+#endif
 	return 0;
 }