Re: [PATCH AUTOSEL 4.4 08/65] btrfs: cleaner_kthread() doesn't need explicit freeze

[Sasha Levin]

On Thu, Oct 25, 2018 at 05:07:29PM +0200, David Sterba wrote:
> On Thu, Oct 25, 2018 at 10:16:08AM -0400, Sasha Levin wrote:
> > From: Jiri Kosina <jkosina@xxxxxxx>
> >
> > [ Upstream commit 838fe1887765f4cc679febea60d87d2a06bd300e ]
> >
> > cleaner_kthread() is not marked freezable, and therefore calling
> > try_to_freeze() in its context is a pointless no-op.
> >
> > In addition to that, as has been clearly demonstrated by 80ad623edd2d
> > ("Revert "btrfs: clear PF_NOFREEZE in cleaner_kthread()"), it's perfectly
> > valid / legal for cleaner_kthread() to stay scheduled out in an arbitrary
> > place during suspend (in that particular example that was waiting for
> > reading of extent pages), so there is no need to leave any traces of
> > freezer in this kthread.
> >
> > Fixes: 80ad623edd2d ("Revert "btrfs: clear PF_NOFREEZE in cleaner_kthread()")
> > Fixes: 696249132158 ("btrfs: clear PF_NOFREEZE in cleaner_kthread()")
> > Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
> > Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> IIRC it was some preparatory work for livepatching.  I did a quick check
> if this is safe for 4.4 and would say yes, but the patch does not fix
> anything so IMO this does not need to go to stable.

Doesn't that also affect hibernation and such?

--
Thanks,
Sasha