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Date: Wed, 25 Feb 2026 15:16:39 +0100
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, brauner@kernel.org, miklos@szeredi.hu,
	bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org
Subject: Re: [PATCH 2/2] iomap: allow NULL swap info bdev when activating
 swapfile
Message-ID: <20260225141639.GB2732@lst.de>
References: <177188733433.3935463.11119081161286211234.stgit@frogsfrogsfrogs> <177188733484.3935463.443855246947996750.stgit@frogsfrogsfrogs> <20260224140118.GB9516@lst.de> <20260224192653.GC13829@frogsfrogsfrogs>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Tue, Feb 24, 2026 at 11:26:53AM -0800, Darrick J. Wong wrote:
> > That sounds pretty sketchy.  How do you make sure that is safe vs
> > memory reclaim deadlocks?  Does someone really need this feature?
> 
> Err, which part is sketchy, specifically?  This patch that adjusts stuff
> in fs/iomap/, or the (much later) patch to fuse-iomap?

The concept of swapping to fuse.

> Obviously this means that the fuse server is granting a longterm layout
> lease to the kernel swapfile code, so it should reply to
> fuse_iomap_begin with a error code if it doesn't want to do that.
> 
> I don't know that anyone really needs this feature, but pre-iomap
> fuse2fs supports swapfiles, as does any other fuse server that
> implements bmap.

Eww, I didn't know people were already trying to support swap to fuse.