Re: Fix SWSUSP & !SWAP

[Andrew Morton]

Pavel Machek <[e-mail]> wrote:
>
> Hi!
> 
> > > No, ext3 will be "unclean" during resume (you can't really unmount it
> > > during suspend!) and r-o mounting of ext3 will replay journal and
> > > cause data corruption.
> > 
> > Sorry, I still don't get it.  Go through the steps for me:
> > 
> > 1) suspend writes pages to disk
> > 
> > 2) machine is shutdown
> > 
> > 3) restart, journal replay
> > 
> > 4) resume reads pages from disk.
> 
> And now you have kernel which expects data still in journal (that was
> state before suspend), but reality on disk is quite different (journal
> was replayed). Data corruption.

swapfiles are not journalled - the swap a_ops write direct to the swapfile's
blocks with submit_bio().  Journal replay wouldn't touch the swapfile.

I can see that locating the swapfile for the resume-time swapon could be a
problem, but the corruption thing still escapes me.