linux-kernel - Re: Root filesystem read access for firmware load during hibernation image writing

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Message-ID: <Zwm4RMDAfMH-ussN@bombadil.infradead.org>
Date: Fri, 11 Oct 2024 16:44:04 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	linux-pm <linux-pm@...r.kernel.org>, linux-kernel@...r.kernel.org,
	Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
	David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
	Russ Weight <russ.weight@...ux.dev>,
	Danilo Krummrich <dakr@...hat.com>
Subject: Re: Root filesystem read access for firmware load during hibernation
 image writing

On Fri, Oct 11, 2024 at 04:39:53PM -0700, Darrick J. Wong wrote:
> On Fri, Oct 11, 2024 at 04:11:49PM -0700, Luis Chamberlain wrote:
> 
> Reads are generally supposed to succeed on a suspended system but if the
> read causes a write (e.g. atime update) they can block just like a write
> would.  So in the end you probably have to cache the firmware blobs in a
> tmpfs or something like that.

The fw cache stuff caches is it in memory to avoid these races on resume.

> > So.. we just now gotta respin the latest effort. I had stopped because
> > I know Darrick had some changes which he needed to get in sooner but
> 
> Do you remember what changes those were?  I don't. :(

Yeah I have a random tree somewhere lemme see...

https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20230507-fs-freeze

Fortunately most of it is coccinelle smpl so should be easy to rebase.

  Luis