linux-kernel - Re: [PATCH v2 6/6] super: add filesystem freezing helpers for suspend and hibernate

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Message-ID: <20250331-postfach-suchaktion-b7f7c696b632@brauner>
Date: Mon, 31 Mar 2025 12:25:34 +0200
From: Christian Brauner <brauner@...nel.org>
To: Jan Kara <jack@...e.cz>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	James Bottomley <James.Bottomley@...senpartnership.com>, mcgrof@...nel.org, hch@...radead.org, david@...morbit.com, 
	rafael@...nel.org, djwong@...nel.org, pavel@...nel.org, peterz@...radead.org, 
	mingo@...hat.com, will@...nel.org, boqun.feng@...il.com
Subject: Re: [PATCH v2 6/6] super: add filesystem freezing helpers for
 suspend and hibernate

On Mon, Mar 31, 2025 at 12:23:04PM +0200, Jan Kara wrote:
> On Sat 29-03-25 09:42:19, Christian Brauner wrote:
> > Allow the power subsystem to support filesystem freeze for
> > suspend and hibernate.
> > 
> > Signed-off-by: Christian Brauner <brauner@...nel.org>
> 
> One comment below. Otherwise feel free to add:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>
> 
> > +void filesystems_thaw(bool hibernate)
> > +{
> > +	__iterate_supers(filesystems_thaw_callback, NULL,
> > +			 SUPER_ITER_UNLOCKED | SUPER_ITER_REVERSE);
> > +}
> 
> I think we should thaw in normal superblock order, not in reverse one? To
> thaw the bottommost filesystem first? The filesystem thaw callback can
> write to the underlying device and this could cause deadlocks...

Yep, I've fixed that already up in vfs-6.16.super yesterday.
Sorry, forgot to mention that here. Thanks for noticing!