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Date: Sun, 28 Apr 2024 20:07:09 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org, Christian Brauner <brauner@kernel.org>,
	Christoph Hellwig <hch@lst.de>, linux-block@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>, linux-btrfs@vger.kernel.org,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 4/7] swapon(2): open swap with O_EXCL
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Sun, Apr 28, 2024 at 11:46:05AM -0700, Linus Torvalds wrote:
> On Sun, 28 Apr 2024 at 11:19, Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > FWIW, pretty much the same can be done with zram - open with O_EXCL and to
> > hell with reopening.  Guys, are there any objections to that?
> 
> Please do. The fewer of these strange "re-open block device" things we
> have, the better.
> 
> I particularly dislike our "holder" logic, and this re-opening is one
> source of nasty confusion, and if we could replace them all with just
> the "O_EXCL uses the file itself as the holder", that would be
> absolutely _lovely_.

The tricky part is blk_holder_ops, and I'm no fonder of it than you are.

Christoph, do you have any plans along those lines for swap devices?
If they are not going to grow holder_ops, I'd say we should switch
to O_EXCL open and be done with that; zram is in the same situation,
AFAICS.

Might be worth a topic at LSF, actually...