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Date: Thu, 4 Apr 2024 07:13:44 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Joseph Salisbury <joseph.salisbury@canonical.com>
Cc: hch@lst.de, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	axboe@kernel.dk, sashal@kernel.org, stable@vger.kernel.org,
	Francis Ginther <francis.ginther@canonical.com>
Subject: Re: [v5.15 Regression] block: rename GENHD_FL_NO_PART_SCAN to
 GENHD_FL_NO_PART
Message-ID: <2024040407-bucket-sank-25a4@gregkh>
References: <924449dc-9b1f-4943-afe3-a68c03aedbb5@canonical.com>
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 <a0819f54-7469-4c94-b567-71f634c84ac1@canonical.com>
 <2024040306-putdown-grain-daf7@gregkh>
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In-Reply-To: <2024040306-putdown-grain-daf7@gregkh>

On Wed, Apr 03, 2024 at 08:40:00PM +0200, Greg KH wrote:
> On Wed, Apr 03, 2024 at 02:06:28PM -0400, Joseph Salisbury wrote:
> > 
> > 
> > On 4/3/24 13:54, Greg KH wrote:
> > > On Wed, Apr 03, 2024 at 01:50:09PM -0400, Joseph Salisbury wrote:
> > > > Hi Christoph,
> > > > 
> > > > A kernel bug report was opened against Ubuntu [0].? This bug is a regression
> > > > introduced in mainline version v5.17-rc1 and made it's way into v5.15 stable
> > > > updates.
> > > > 
> > > > The following commit was identified as the cause of the regression in 5.15:
> > > > 
> > > > c6ce1c5dd327 ("block: rename GENHD_FL_NO_PART_SCAN to GENHD_FL_NO_PART")
> > > How is renaming a define a "regression"?
> > The "regression" is experienced after upgrading to the kernel to the version
> > that introduced this commit.
> > The v5.15.131 kernel works as expected, upgrading the kernel to v5.15.132
> > breaks behavior that worked in a prior kernel version.
> > Reverting commit c6ce1c5dd327 in v5.15.132 allows the experience to be as
> > before in v5.15.131.
> 
> What "experience" are you talking about here?  Please be specific.  What
> exactly "broke", what is the build error that happens?
> 
> > > > I was hoping to get your feedback, since you are the patch author. Is the
> > > > best approach to revert this commit, since many third parties rely on the
> > > > name being GENHD_FL_NO_PART_SCAN in kernel headers?
> > > External kernel modules are never an issue.  Is this a userspace thing?
> > > 
> > > >  ?Is there a specific need that you know of that requires this commit
> > > > in the 5.15 and earlier stable kernels?
> > > Yes.  And Christoph did not do the backport, so I doubt he cares :)
> > > 
> > > Again, what in-kernel issue is caused by this?
> > 
> > Third party code that relies on the kernel-headers will no longer compile
> > due to the name change.? Should we not care if we break things, even in
> > userspace?
> 
> Is this userspace, or is it kernel drivers?
> 
> If kernel drivers, you know that there  s no stable kernel api, we
> rename and change things all the time, even in stable kernel trees, for
> good reasons (see the set of patches that were applied that contained
> this change.)  Do you want to have unfixed security issues, or do you
> want a secure kernel that happens to rename variables at times?

Given the lack of response, I am going to assume that this means you are
referring to out-of-tree kernel code and this is not a real "regression"
at all.

greg k-h