linux-kernel - Re: [PATCH AUTOSEL 4.4 08/65] btrfs: cleaner

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Message-ID: <20181025200751.GB1693@sasha-vm>
Date:   Thu, 25 Oct 2018 16:07:51 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     dsterba@...e.cz, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH AUTOSEL 4.4 08/65] btrfs: cleaner_kthread() doesn't need
 explicit freeze

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@...e.cz>
>>
>> [ 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@...e.cz>
>> Signed-off-by: David Sterba <dsterba@...e.com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>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