linux-kernel - Re: [PATCH] fs: allow nesting with FREEZE

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Message-ID: <20250509-unzucht-gestundet-8633defb4c9e@brauner>
Date: Fri, 9 May 2025 12:38:29 +0200
From: Christian Brauner <brauner@...nel.org>
To: Jan Kara <jack@...e.cz>
Cc: linux-fsdevel@...r.kernel.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, 
	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] fs: allow nesting with FREEZE_EXCL

On Wed, May 07, 2025 at 01:18:34PM +0200, Jan Kara wrote:
> On Fri 04-04-25 12:24:09, Christian Brauner wrote:
> > If hibernation races with filesystem freezing (e.g. DM reconfiguration),
> > then hibernation need not freeze a filesystem because it's already
> > frozen but userspace may thaw the filesystem before hibernation actually
> > happens.
> > 
> > If the race happens the other way around, DM reconfiguration may
> > unexpectedly fail with EBUSY.
> > 
> > So allow FREEZE_EXCL to nest with other holders. An exclusive freezer
> > cannot be undone by any of the other concurrent freezers.
> > 
> > Signed-off-by: Christian Brauner <brauner@...nel.org>
> 
> This has fallen through the cracks in my inbox but the patch now looks good
> to me. Maybe we should fold it into "fs: add owner of freeze/thaw" to not
> have strange intermediate state in the series?

Done.