linux-kernel - Re: [PATCH 0/6] power: wire-up filesystem freeze/thaw with suspend/resume

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Message-ID: <20250401141407.GE5880@noisy.programming.kicks-ass.net>
Date: Tue, 1 Apr 2025 16:14:07 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, jack@...e.cz, rafael@...nel.org,
	Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	mcgrof@...nel.org, hch@...radead.org, david@...morbit.com,
	djwong@...nel.org, pavel@...nel.org, mingo@...hat.com,
	will@...nel.org, boqun.feng@...il.com
Subject: Re: [PATCH 0/6] power: wire-up filesystem freeze/thaw with
 suspend/resume

On Tue, Apr 01, 2025 at 02:32:45AM +0200, Christian Brauner wrote:
> The whole shebang can also be found at:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/log/?h=work.freeze
> 
> I know nothing about power or hibernation. I've tested it as best as I
> could. Works for me (TM).
> 
> I need to catch some actual sleep now...
> 
> ---
> 
> Now all the pieces are in place to actually allow the power subsystem to
> freeze/thaw filesystems during suspend/resume. Filesystems are only
> frozen and thawed if the power subsystem does actually own the freeze.

Urgh, I was relying on all kthreads to be freezable for live-patching:

  https://lkml.kernel.org/r/20250324134909.GA14718@noisy.programming.kicks-ass.net

So I understand the problem with freezing filesystems, but can't we
leave the TASK_FREEZABLE in the kthreads? The way I understand it, the
power subsystem will first freeze the filesystems before it goes freeze
threads anyway. So them remaining freezable should not affect anything,
right?