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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20181026105710.GD2015@sasha-vm>
Date:   Fri, 26 Oct 2018 06:57:10 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     dsterba@...e.cz, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.4 08/65] btrfs: cleaner_kthread() doesn't need
 explicit freeze

On Fri, Oct 26, 2018 at 08:58:57AM +0200, Jiri Kosina wrote:
>On Thu, 25 Oct 2018, Sasha Levin wrote:
>
>> >> 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
>> >> Fixes: 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?
>
>This patch just removes pointless try_to_freeze(), that's guaranteed not
>to do anything and return immediately, as the btrfs kthread is not
>freezable.
>So I don't think it's needed in stable; the semantics is equivalent before
>and after.

Gotcha. I'll drop it. Thank you!

--
Thanks,
Sasha