Re: Patch "md: call del_gendisk in control path" has been added to the 6.6-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Aug 18, 2025 at 02:26:23PM +0800, Yu Kuai wrote:
> Hi,
> 
> 在 2025/08/18 13:55, Greg KH 写道:
> > On Mon, Aug 18, 2025 at 09:03:39AM +0800, Yu Kuai wrote:
> > > Hi,
> > > 
> > > 在 2025/08/17 22:18, Sasha Levin 写道:
> > > > This is a note to let you know that I've just added the patch titled
> > > > 
> > > >       md: call del_gendisk in control path
> > > > 
> > > > to the 6.6-stable tree which can be found at:
> > > >       http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > > > 
> > > > The filename of the patch is:
> > > >        md-call-del_gendisk-in-control-path.patch
> > > > and it can be found in the queue-6.6 subdirectory.
> > > > 
> > > > If you, or anyone else, feels it should not be added to the stable tree,
> > > > please let <stable@vger.kernel.org> know about it.
> > > > 
> > > > 
> > > This patch should be be backported to any stable kernel, this change
> > > will break user tools mdadm:
> > > 
> > > https://lore.kernel.org/all/f654db67-a5a5-114b-09b8-00db303daab7@redhat.com/
> > 
> > Is it reverted in Linus's tree?
> > 
> 
> No, we'll not revert it, this is an improvement. In order to keep user
> tools compatibility, we added a switch in the kernel. As discussed in
> the thread, for old tools + new kernel, functionality is the same,
> however, there will be kernel warning about deprecated behaviour to
> inform user upgrading user tools.
> 
> However, I feel this new warning messages is not acceptable for
> stable kernels.

Why?  What is so special about stable kernels that taking the same
functionality in newer kernels is not ok?

Why not just "warn" the same here if you want to fix an issue where
userspace should be also updating some tools.  As long as you aren't
breaking anything, it should be fine, right?

Or are you breaking existing workflows?  You should be able to take a
new kernel without any userspace changes and all should work the same.
Why make new kernel users change userspace tools at all?

thanks,

greg k-h