Hi!
> > | Update suspend documentation.
> > |
> > | Signed-off-by: Pavel Machek <[email protected]>
> > |
> > | ---
> > |
> > | diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
> > | --- a/Documentation/power/swsusp.txt
> > | +++ b/Documentation/power/swsusp.txt
> > | @@ -318,3 +318,10 @@ As a rule of thumb use encrypted swap to
> > | system is shut down or suspended. Additionally use the encrypted
> > | suspend image to prevent sensitive data from being stolen after
> > | resume.
> > | +
> > | +Q: Why we cannot suspend to a swap file?
> >
> > Q: Why can't we suspend to a swap file?
> > or
> > Q: Why can we not suspend to a swap file?
> >
> > | +
> > | +A: Because accessing swap file needs the filesystem mounted, and
> > | +filesystem might do something wrong (like replaying the journal)
> > | +during mount. [Probably could be solved by modifying every filesystem
> > | +to support some kind of "really read-only!" option. Patches welcome.]
>
> This is wrong. Suspend2 has supported writing to a swap file for a long
> time (since 1.0), without requiring the filesystem to be mounted when
> resuming. We just need to store the bdev and block numbers in the image
> header.
Uh, and then you pass something like resume=/dev/hda5@BLOCKID on
command line? Okay, that could work.
Does this look fair?
Q: Why can't we suspend to a swap file?
A: Because accessing swap file needs the filesystem mounted, and
filesystem might do something wrong (like replaying the journal)
during mount.
There are few ways to get that fixed:
1) Probably could be solved by modifying every filesystem to support
some kind of "really read-only!" option. Patches welcome.
2) suspend2 gets around that by storing absolute positions in on-disk
image, with resume parameter pointing directly to suspend header.
Pavel
--
teflon -- maybe it is a trademark, but it should not be.
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