2006/11/28, Stefan Seyfried <[EMAIL PROTECTED]>: > On Tue, Nov 28, 2006 at 10:43:51AM -0500, Alan Stern wrote: > > On Tue, 28 Nov 2006, Daniel Drake wrote: > > > > > Hi, > > > > > > I have some questions about this text in Documentation/power/swsusp.txt: > > > > > > * If you touch anything on disk between suspend and resume... > > > * ...kiss your data goodbye. > > > > > > It's obvious that this is a bad idea but I'm interested in the details. > > > I'm working with the userspace suspend-to-disk tools in this case. > > > > > > Specifically, where it says "kiss your data goodbye" is that saying that > > > upon next resume you would lose data in open and unsaved documents (i.e. > > > session data), or does it mean that your root partition is effectively > > > destroyed? > > > > Almost anything could happen, depending on the type of filesystem and the > > nature of the changes you make to the disk. > > ACK. > > > > Is the danger only in touching the swap partition where the resume data > > > is saved, or is mounting any of the filesystems that are mounted in the > > > suspended session dangerous? > > > > Touching _anything_ is dangerous. > > ACK. > > > > How dangerous? > > > > Like I said above, it depends. > > Let's put it this way. In the early days of me trying software suspend > (around 2.6.$early), i once suspended a machine, wanted to resume but > selected the wrong kernel on resume. Machine booted. I noticed this and > immediately powered the machine off (the fs had already been mounted). > Then i tried to resume. > Afterwards i had an interesting session with "reiserfsck --rebuild-tree" > and other funny tools you don't want to use. I was just lucky, that i > always have a current backup, since sorting out the useful parts of my > home directory in lost+found would not have been a funny job. And /home > was less affected than /, since / was also written to during boot. >
In suspend2 (now I will get flamed...) there is a nice feature that warns that you are trying to resume with a wrong kernel, that lets you reboot the machine without losing anything.... > > > Are we talking instant loss > > > of entire filesystem, or just a chance that some files will be > > > corrupted? > > If you are lucky, the filesytem is just instantly screwed. > If you are unlucky, you get silent corruption that keeps growing until > your backups are phased out and you finally start noticing it. > > > File corruption is the most likely outcome, but I wouldn't say that > > losing an entire filesystem is impossible. You'd have to try pretty hard, > > though. Running mkfs would certainly do it. :-) > > > > > When does the corruption happen - during mount after suspend > > > but before resume, or during resume after suspend+modifications? > > > > Corruption occurs when you write to the disk. Note the the disk doesn't > > have to be mounted. In addition, even if you mount an ext3 filesystem > > read-only, the fs code will play back the journal -- thereby writing to > > the disk. > > > > What kind of dangers are associated with suspending to disk, modifying > > > data on disk but then *not* resuming (doing a complete boot, e.g. > > > recreating the swap partition to prevent resume from being attempted)? > > This case is just like "powered off hard by tripping the power cord", > maybe even less dramatic since the disk buffers will at least be flushed > by swsusp. The filesystem will be dirty, the fsck on boot will probably > just fix it (i have had no real problems after a hard shutdown for a > long time). > > > > The context I'm thinking of is an engineer called out to repair a broken > > > system. This system will not boot, lets say the RAM is screwed and the > > > kernel hangs/panics during early init (before any resuming is > > > attempted). > > > > > > Without touching the disks, there is no way of knowing if the system was > > > shut down fully or suspended-to-disk on last shutdown. > > He just has to look at the end of the first page of the swap partition > for the signature :-) > > So it is a good idea to tell the engineer to do "mkswap" on the swap > partition before putting the disk into the replacement hardware. > > -- > Stefan Seyfried > QA / R&D Team Mobile Devices | "Any ideas, John?" > SUSE LINUX Products GmbH, Nürnberg | "Well, surrounding them's out." > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Suspend-devel mailing list > Suspend-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/suspend-devel > ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Suspend-devel mailing list Suspend-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/suspend-devel
