Messages in this thread | | | Subject | Re: [PATCH] PM / hibernate: Introduce snapshot test mode for hibernation | From | Chen Yu <> | Date | Thu, 14 Jul 2016 18:44:49 +0800 |
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Hi,
On 2016年07月14日 06:18, Rafael J. Wysocki wrote: > On Thu, Jul 14, 2016 at 12:00 AM, Rafael J. Wysocki <rafael@kernel.org> wrote: >> On Wed, Jul 13, 2016 at 11:45 PM, Pavel Machek <pavel@ucw.cz> wrote: >>> On Wed 2016-07-13 22:44:24, Rafael J. Wysocki wrote: >>>> On Wed, Jul 13, 2016 at 10:26 PM, Pavel Machek <pavel@ucw.cz> wrote: >>>>> On Wed 2016-07-13 22:04:27, Rafael J. Wysocki wrote: >>>>>> On Wed, Jul 13, 2016 at 7:01 PM, Pavel Machek <pavel@ucw.cz> 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? >> OK, there is a bug. >> >> The thawing of user space is potentially dangerous, so in the >> "snapshot" test mode hibernate() should just call >> free_basic_memory_bitmaps() and from there invoke the code below the >> Check_image label in software_resume(), roughly. > Or rather call free_basic_memory_bitmaps() and > unlock_device_hotplug(), then do swsusp_check() and invoke the code > starting with the "PM: Loading hibernation image.\n" message in > software_resume(). OK, I've used this solution and sent a v3 out. thanks! > > Thanks, > Rafael
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