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

From: Sasha Levin
Date: Thu Oct 25 2018 - 16:07:56 EST

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?