linux-kernel - Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release

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Date: Fri, 24 May 2024 08:21:05 +0200
From: David Hildenbrand <david@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Donet Tom <donettom@...ux.ibm.com>, Shuah Khan <shuah@...nel.org>,
 Matthew Wilcox <willy@...radead.org>, Tony Battersby
 <tonyb@...ernetics.com>, linux-mm@...ck.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Ritesh Harjani <ritesh.list@...il.com>, Mike Rapoport <rppt@...nel.org>,
 Muchun Song <songmuchun@...edance.com>, stable@...r.kernel.org
Subject: Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during
 __bio_release_pages()

On 24.05.24 04:57, Andrew Morton wrote:
> On Thu, 23 May 2024 22:40:25 +0200 David Hildenbrand <david@...hat.com> wrote:
> 
>>> You have stable@...r.kernel.org in the mail headers, so I assume you're
>>> proposing this for backporting.  When doing this, please include
>>>
>>> Cc: <stable@...r.kernel.org>
>>>
>>> in the changelog footers and also include a Fixes: target.  I'm
>>> assuming the suitable Fixes: target for this patch is 38b43539d64b?
>>
>> This adds a new selfest to make sure what was fixed (and backported to
>> stable) remains fixed.
> 
> Sure.  But we should provide -stable maintainers guidance for "how far
> back to go".  There isn't much point in backporting this into kernels
> where it's known to fail!

I'm probably missing something important.

1) It's a test that does not fall into the common stable kernels 
categories (see Documentation/process/stable-kernel-rules.rst).

2) If it fails in a kernel *it achieved its goal* of highlighting that 
something serious is broken.

> 
> I'm still thinking that we want this in kernels which have 38b43539d64b?

To hide that the other kernels are seriously broken and miss that fix?

Really (1) this shouldn't be backported. I'm not even sure it should be 
a selftest (sounds more like a reproducer that we usually attach to 
commits, but that's too late). And if people care about backporting it, 
(2) you really want this test to succeed everywhere. Especially also to 
find kernels *without* 38b43539d64b

-- 
Cheers,

David / dhildenb