Sender: ming.lei@xxxxxxxxxx
Subject: Re: [PATCH 07/15] block: move blk_unregister_queue() & device_del() after freeze wait
Message-Id: <Z_3D0PZWolXUdXnK@fedora>
Recipient: yangpanfei@xxxxxxxxx
--- Begin Message ---
On Mon, Apr 14, 2025 at 08:19:10AM +0200, Christoph Hellwig wrote:
> On Thu, Apr 10, 2025 at 09:30:19PM +0800, Ming Lei wrote:
> > Move blk_unregister_queue() & device_del() after freeze wait, and prepare
> > for unifying elevator switch.
> >
> > This way is just fine, since bdev has been unhashed at the beginning of
> > del_gendisk(), both blk_unregister_queue() & device_del() are dealing
> > with kobject & debugfs thing only.
>
> While I believe this is the right thing to do, moving the freeze wait
> caused issues in the past, so be careful. Take a look at:
>
> commit 4c66a326b5ab784cddd72de07ac5b6210e9e1b06
> Author: Christoph Hellwig <hch@xxxxxx>
> Date: Mon Sep 19 16:40:49 2022 +0200
>
> Revert "block: freeze the queue earlier in del_gendisk"
Yeah, I know this story.
If it is triggered again with this patch, I will help to root cause.
The last thing we still can do is to just moving blk_unregister_queue()
after queue is frozen, or even elevator tear down. It is allowed to delete
children kobjects after their parent is removed. Just the KOBJ_REMOVE
event need to be ordered.
Thanks,
Ming
--- End Message ---
