linux-ext4 - Re: [PATCH 1/1] iomap: allow NULL swap info bdev when activating swapfile

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Message-ID: <20251029084048.GA32095@lst.de>
Date: Wed, 29 Oct 2025 09:40:48 +0100
From: Christoph Hellwig <hch@....de>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: miklos@...redi.hu, brauner@...nel.org, linux-ext4@...r.kernel.org,
	hch@....de, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/1] iomap: allow NULL swap info bdev when activating
 swapfile

On Tue, Oct 28, 2025 at 05:44:26PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@...nel.org>
> 
> All current users of the iomap swapfile activation mechanism are block
> device filesystems.  This means that claim_swapfile will set
> swap_info_struct::bdev to inode->i_sb->s_bdev of the swap file.
> 
> However, in the future there could be fuse+iomap filesystems that are
> block device based but don't set s_bdev.  In this case, sis::bdev will
> be set to NULL when we enter iomap_swapfile_activate, and we can pick
> up a bdev from the first iomap mapping that the filesystem provides.

Could, or will be?  I find the way the swapfiles work right now
disgusting to start with, but extending that bypass to fuse seems
even worse.