From: "Darrick J. Wong" Subject: Re: [PATCH] vfs: freeze filesystems just prior to reboot Date: Fri, 19 May 2017 12:01:15 -0700 Message-ID: <20170519190115.GJ4519@birch.djwong.org> References: <20170519002032.GA21202@birch.djwong.org> <1495202431.1896310.982081664.066926F8@webmail.messagingengine.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: xfs , linux-fsdevel , linux-ext4 To: Colin Walters Return-path: Content-Disposition: inline In-Reply-To: <1495202431.1896310.982081664.066926F8@webmail.messagingengine.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Fri, May 19, 2017 at 10:00:31AM -0400, Colin Walters wrote: > On Thu, May 18, 2017, at 08:20 PM, Darrick J. Wong wrote: > > > Therefore, add a reboot hook to freeze all filesystems (which in general > > will induce ext4/xfs/btrfs to checkpoint the log) just prior to reboot. > > This is an unfortunate and insufficient workaround for multiple layers > > of inadequate external software, but at least it will reduce boot time > > surprises for the "OS updater failed to disengage the filesystem before > > rebooting" case. > > As a maintainer of one of those userspace tools > (https://github.com/ostreedev/ostree), which I don't think is the one > in question here, but likely has the same issue - I'd like to have > some sort of API to fix this - maybe flush the journal *without* > remounting r/o? The convention (at least among ext4 and xfs) is that fs freeze should be checkpointing the journal. > Unlike the case you're talking about with rebooting into a special > update mode, libostree constructs a new root with hardlinks while > the system is running. Hence, system downtime is just reboot, like > dual-partition update systems, except we're more flexible. > > Although hm...I guess an API to flush the journal would only narrow > the race. > > Is the single partition case really just doomed? Probably. TBH given the current behavior of grub, I would always have a separate /boot to minimize the amount it's allowed to touch. :) --D > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html