From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH] PM / hibernate: Introduce snapshot test mode for hibernation Date: Wed, 13 Jul 2016 23:45:46 +0200 Message-ID: <20160713214546.GA26692@amd> References: <1467873658-31986-1-git-send-email-yu.c.chen@intel.com> <20160713095005.GA27870@amd> <578615D5.3060501@intel.com> <20160713102156.GA14505@atrey.karlin.mff.cuni.cz> <57861A70.9090606@intel.com> <20160713170123.GA13546@amd> <20160713202611.GA32111@amd> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:52990 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbcGMVpv (ORCPT ); Wed, 13 Jul 2016 17:45:51 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Chen Yu , Linux PM , "Rafael J. Wysocki" , Len Brown , Linux Kernel Mailing List On Wed 2016-07-13 22:44:24, Rafael J. Wysocki wrote: > On Wed, Jul 13, 2016 at 10:26 PM, Pavel Machek wrote: > > On Wed 2016-07-13 22:04:27, Rafael J. Wysocki wrote: > >> On Wed, Jul 13, 2016 at 7:01 PM, Pavel Machek wrote: > >> > Hi! > >> > > >> >> >>and then swapon the swap device, and do a testing. This should be safer? > >> >> >Yeah, that's the way. Read-only root is other option. > >> >> > > >> >> >>>I guess updating documentation would be welcome from my side, > >> >> >>>otherwise it should be ok. > >> >> >>OK, I'll update the documents. > >> >> >Just add fat warning into the documentation. > >> >> OK. > >> > > >> > Actually... If you could add > >> > > >> > printk(KERN_ALERT "Hibernation image written. If you have any > >> > filesystems mounted read-write and attempt to resume, you'll corrupt > >> > your data. To prevent that, remove the hibernation image.\n") > >> > > >> > ...I guess that would save someone's filesystem. (Yes, very high > >> > loglevel. If you attempt to do this from anything else then singleuser > >> > or initrd, you are asking for problems, so... lets make sure user sees > >> > it.) > >> > >> Please see the new version of this patch: > >> https://patchwork.kernel.org/patch/9226837/ > > > > New version changes nothing, right? You still need to be sure > > filesystems are not mounted r/w. So I would still like to see printk() > > with warning. > > It shouldn't matter how they are mounted, because the contents of > persistent storage don't change. @@ -721,6 +724,9 @@ int hibernate(void) atomic_inc(&snapshot_device_available); Unlock: unlock_system_sleep(); + if (snapshot_test) + software_resume(); + return error; } Aha, I see, immediate wakeup here. Makes sense. ... ... No. AFAICT, freezer is used in hibernation_snapshot, which means at Unlock:, kernel threads are running; software_resume() freezes them again, but they had chance to run and potentially corrupt the persistent storage... right? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html