Messages in this thread | | | Date | Wed, 26 Sep 2007 16:30:36 -0400 | Subject | Re: [RFC][PATCH 1/2 -mm] kexec based hibernation -v3: kexec jump | From | (Joseph Fannin) |
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On Fri, Sep 21, 2007 at 11:45:12AM +0200, Pavel Machek wrote: > Hi! > > > > > > Sounds doable, as long as you can cope with long command lines (which > > > shouldn't be a biggie). (If you've got a swapfile or parts of a swap > > > partition already in use, it can be quite fragmented). > > > > Hmm. This is an interesting problem. Sharing a swap file or a swap > > partition with the actual swap of user space pages does seem to be > > a limitation of this approach. > > > > Although the fact that it is simple to write to a separate file may > > be a reasonable compensation. > > I'm not sure how you'd write it to a separate file. Notice that kjump > kernel may not mount journalling filesystems, not even > read-only. (Ext3 replays journal in that case). You could pass block > numbers from the original kernel...
The ext3 thing is a bug, the case for which I don't think has been adequately explained to the ext[34] folks. There should be at least a no_replay mount flag available, or something. It has ramifications for more than just hibernation.
And yeah, I'm gonna bring up the swap files thing again. If you can hibernate to a swap file, you can hibernate to a dedicated hibernation file, and vice versa.
If you can't hibernate to a swap file, then swap files are effectively unsupported for any system you might want to hibernate. <handwave> I wonder what embedded folks would think about that </handwave>.
But, in my ignorance, I'm not sure even fixing the ext3 bug will guarantee you consistent metadata so that you can handle a swap/hibernate file. You can do a sync(), but how do you make that not race against running processes without the freezer, or blkdev snapshots?
I guess uswsusp and the-patch-previously-known-as-suspend2 handle this somehow, though.
(It's that same ignorance that has me waiting for someone with established credit with kernel people to make that argument for the ext3 bug, so I can hang my own reasons for thinking that it's bad off of theirs).
-- Joseph Fannin jfannin@gmail.com
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