From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from www262.sakura.ne.jp ([202.181.97.72]:65395 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731215AbfHAVNf (ORCPT ); Thu, 1 Aug 2019 17:13:35 -0400 Subject: Re: [PATCH] fs: xfs: xfs_log: Don't use KM_MAYFAIL at xfs_log_reserve(). References: <20190729215657.GI7777@dread.disaster.area> <1564653995-9004-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20190801185057.GT30113@42.do-not-panic.com> From: Tetsuo Handa Message-ID: Date: Fri, 2 Aug 2019 06:13:12 +0900 MIME-Version: 1.0 In-Reply-To: <20190801185057.GT30113@42.do-not-panic.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Luis Chamberlain Cc: linux-xfs@vger.kernel.org, Dave Chinner , Brian Foster On 2019/08/02 3:50, Luis Chamberlain wrote: > That's quite an opaque commit log for what started off as a severe email > thread of potential leak of information. As such, can you expand on this > commit log considerably to explain the situation a bit better? Your > initial thread here provided much clearer evidence of the issue. As-is > this commit log tells the reader *nothing* about the potential harm in > not applying this patch. > > You had mentioned you identified this issue present on at least > 4.18 till 5.3-rc1. So, I'm at least inclined to consider this for > stable for at least v4.19. > > However, what about older kernels? Now that you have identified > a fix, were the flag changed in prior commits, is it a regression > that perhaps added KM_MAYFAIL at some point? I only checked 4.18+ so that RHEL8 will backport this patch. According to Brian Foster, commit eb01c9cd87 ("[XFS] Remove the xlog_ticket allocator") ( https://git.kernel.org/linus/eb01c9cd87 ) which dates back to April 2008 added KM_MAYFAIL flag for this allocation - buf = (xfs_caddr_t) kmem_zalloc(PAGE_SIZE, KM_SLEEP); + tic = kmem_zone_zalloc(xfs_log_ticket_zone, KM_SLEEP|KM_MAYFAIL); though Dave Chinner thinks that the log ticket rework is irrelevant. Do we need to find which commit made this problem visible?