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Date: Mon, 6 Nov 2023 10:56:57 +0100
From: Christian Brauner <brauner@kernel.org>
To: Qu Wenruo <wqu@suse.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	Josef Bacik <josef@toxicpanda.com>,
	Qu Wenruo <quwenruo.btrfs@gmx.com>,
	Amir Goldstein <amir73il@gmail.com>, Jan Kara <jack@suse.cz>,
	Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
	linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 0/3] fanotify support for btrfs sub-volumes
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In-Reply-To: <1d08a205-b2c5-4276-b271-088facc142ea@suse.com>

> Another thing is, the st_dev situation has to be kept, as there are too many
> legacy programs that relies on this to distinguish btrfs subvolume
> boundaries, this would never be changed unfortunately, even if we had some
> better solution (like the proposed extra subvolid through statx).

It would retain backwards compatibility as userspace would need to
explicitly query for STATX_SUBVOLUME otherwise they get they fake
st_dev.

> Which I believe the per-subvolume-vfsmount and the automount behavior for
> subvolume can help a lot.

Very much opposed to this at this point. I've seen the code for this in
the prior patchset and it's implication nothing about this makes me want
this.