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Date: Mon, 18 Mar 2024 09:33:35 +0100
From: Christian Brauner <brauner@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>, 
	"Darrick J. Wong" <djwong@kernel.org>, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH] fs,block: get holder during claim
Message-ID: <20240318-begierde-ehedrama-a3b57393e496@brauner>
References: <20240314165814.tne3leyfmb4sqk2t@quack3>
 <20240315-freibad-annehmbar-ca68c375af91@brauner>
 <ZfdYX3-_53txEYTa@infradead.org>
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In-Reply-To: <ZfdYX3-_53txEYTa@infradead.org>

On Sun, Mar 17, 2024 at 01:53:51PM -0700, Christoph Hellwig wrote:
> On Fri, Mar 15, 2024 at 02:23:07PM +0100, Christian Brauner wrote:
> > Now that we open block devices as files we need to deal with the
> > realities that closing is a deferred operation. An operation on the
> > block device such as e.g., freeze, thaw, or removal that runs
> > concurrently with umount, tries to acquire a stable reference on the
> > holder. The holder might already be gone though. Make that reliable by
> > grabbing a passive reference to the holder during bdev_open() and
> > releasing it during bdev_release().
> 
> Looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> does bcachefs also need a fix for it's holder ops?  Or does it get to
> keep the pieces as it has it's own NULL holder_ops and obviously doens't
> care about getting any of this right?

It has empty holder ops and so is behaving equivalent too having NULL
holder ops. IOW, the block layer cannot access the holder.