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Date: Mon, 18 Dec 2023 13:22:15 +0100
From: Christian Brauner <brauner@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
	David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org,
	Eric Biggers <ebiggers@kernel.org>
Subject: Re: [PATCH 2/5] btrfs: call btrfs_close_devices from ->kill_sb
Message-ID: <20231218-engpass-vorladung-8a41c369480d@brauner>
References: <20231218044933.706042-1-hch@lst.de>
 <20231218044933.706042-3-hch@lst.de>
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In-Reply-To: <20231218044933.706042-3-hch@lst.de>

On Mon, Dec 18, 2023 at 05:49:30AM +0100, Christoph Hellwig wrote:
> blkdev_put must not be called under sb->s_umount to avoid a lock order
> reversal with disk->open_mutex once call backs from block devices to
> the file system using the holder ops are supported.  Move the call

With what's in vfs.super that part isn't necessary anymore. Locking
order is guaranteed so that s_umount ranks above open_mutex as before as
you know ofc. And we've got lockdep asserts everywhere so that lockdep
would complain immediately. It's still nicer imho to close devices in
->kill_sb() but it isn't needed anymore.

btrfs folks might want to consider pulling in vfs.super. It's been
stable on v6.7-rc1 for weeks and I won't change it anymore. Last change
on that branch is from Tue, 28 November.