From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:48212 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726547AbeJCTYA (ORCPT ); Wed, 3 Oct 2018 15:24:00 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B166D3081D83 for ; Wed, 3 Oct 2018 12:35:47 +0000 (UTC) Received: from odin.usersys.redhat.com (unknown [10.40.205.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0CE625D77E for ; Wed, 3 Oct 2018 12:35:46 +0000 (UTC) From: Carlos Maiolino Subject: [PATCH 0/2] xfs stats fixes Date: Wed, 3 Oct 2018 14:35:35 +0200 Message-Id: <20181003123537.30965-1-cmaiolino@redhat.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: linux-xfs@vger.kernel.org Hi, this week I found a bug in the code for xqmstat file in procfs, caused by wrong offsets while reading the __xfsstats structure fields in xqmstat_proc_show. This patchset aims to fix the bug (patch 1) and add a way to reduce the likelyhood of creating the same error again. xqmstat_proc_show() uses a loop to walk through the quota-specific fields in __xfsstats when printing the information. The problem is, since the start/end offsets are hardcoded, any update to __xfsstats may also require an update on the start offset in xqmstat_proc_show(). I decided to split it into two patches, because I think it is easier to let the bugfix itself in a separated patch, and the approach on how to avoid it in the future can be discussed in a separated patch. My first idea was to try to add a method to check it at compile time, and I spent some time discussing with Eric what would be the best way to avoid this problem in the future. We end up with an possible solution using offsetof() and a new constant in xfs_stats.h to properly check the offsets at compile time. Although, after giving it some extra thought, I found it better to only use a new constant to mark the start of xqmstat in xfs_stats.h and not add any fancy calculation in xqmstat_proc_show itself. History told me that all updates to __xfsstats and its respective content/uses, were properly done when needed, only the xqmstat was left behind because it's unusual direct usage of the offset markers. So, I believe that the addition of a new marker to specify the start offset of the quota stat fields is enough to avoid future problems here, once no more changes will be needed in xqmstat code whenever __xfsstats requires to be updated. My idea though is still to move this file to sysfs together with the rest of statistic code, but by now, I believe we should fix this bug. Comments? Cheers. Carlos Maiolino (2): xfs: Fix xqmstats offsets in /proc/fs/xfs/xqmstat xfs: Add new constant to mark start of xqmstat fs/xfs/xfs_stats.c | 2 +- fs/xfs/xfs_stats.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) -- 2.17.1