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Date: Mon, 14 Oct 2024 08:10:19 +0200
From: Christoph Hellwig <hch@lst.de>
To: Kent Overstreet <kent.overstreet@linux.dev>
Cc: linux-bcachefs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] bcachefs: Fix sysfs warning in fstests generic/730,731
Message-ID: <20241014061019.GA20775@lst.de>
References: <20241012184239.3785089-1-kent.overstreet@linux.dev>
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In-Reply-To: <20241012184239.3785089-1-kent.overstreet@linux.dev>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Sat, Oct 12, 2024 at 02:42:39PM -0400, Kent Overstreet wrote:
> sysfs warns if we're removing a symlink from a directory that's no
> longer in sysfs; this is triggered by fstests generic/730, which
> simulates hot removal of a block device.
> 
> This patch is however not a correct fix, since checking
> kobj->state_in_sysfs on a kobj owned by another subsystem is racy.
> 
> A better fix would be to add the appropriate check to
> sysfs_remove_link() - and sysfs_create_link() as well.

The proper fix is to not link to random other subsystems with
object lifetimes you can't know.  I'm not sure why you think adding
this link was ever allowed.