Re: 5.13.2-rc and others have many not for stable

From: Mel Gorman <mgorman@techsingularity.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Sasha Levin <sashal@kernel.org>, Michal Hocko <mhocko@kernel.org>,
	Hugh Dickins <hughd@google.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	stable@vger.kernel.org
Subject: Re: 5.13.2-rc and others have many not for stable
Date: Thu, 15 Jul 2021 11:39:44 +0100	[thread overview]
Message-ID: <20210715103944.GQ3809@techsingularity.net> (raw)
In-Reply-To: <YO7lZpqC4xrMPXQg@kroah.com>

On Wed, Jul 14, 2021 at 03:23:50PM +0200, Greg Kroah-Hartman wrote:
> On Wed, Jul 14, 2021 at 11:18:14AM +0200, Greg Kroah-Hartman wrote:
> > On Tue, Jul 13, 2021 at 06:28:13PM -0700, Andrew Morton wrote:
> > > On Tue, 13 Jul 2021 08:31:57 +0200 Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> > > >  So far, all automated testing seems to
> > > > show that there are no regressions in these releases with these commits
> > > > in them.  If there was a problem, how would it show up?
> > > > 
> > > > And as far as I know, mm/ stuff is still not triggered by the AUTOSEL
> > > > bot, but that is not what caused this commit to be added to a stable
> > > > release.
> > > > 
> > > > Trying to keep a "do not apply" list for Fixes: tags only is much harder
> > > > for both of us as we do these semi-manually and review them
> > > > individually.  Trying to remember what subsystem only does Fixes tags
> > > > yet really doesn't mean it is an impossible task.
> > > 
> > > Well, it shouldn't be super hard to skip all patches which have Fixes:,
> > > Signed-off-by:akpm and no cc:stable?
> > 
> > Ok, I will do this now (goes and writes this down...)
> > 
> > But it really feels odd that you all take the time to add a "Hey, this
> > fixes this specific commit!" tag in the changelog, yet you do not
> > actually want to go and fix the kernels that have that commit in it.
> > This is an odd signal to others that watch the changelogs for context
> > clues.  Perhaps you might not want to do that anymore.
> 
> I looked at some of these patches and it seems really odd to me that you
> all are marking them with Fixes: tags, but do not want them backported.
> 
> First example is babbbdd08af9 ("mm/huge_memory.c: don't discard hugepage
> if other processes are mapping it")
> 
> Why is this not ok to backport?
> 
> Also what about e6be37b2e7bd ("mm/huge_memory.c: add missing read-only
> THP checking in transparent_hugepage_enabled()")?
> 
> And 41eb5df1cbc9 ("mm: memcg/slab: properly set up gfp flags for objcg
> pointer array")?
> 
> And 6acfb5ba150c ("mm: migrate: fix missing update page_private to
> hugetlb_page_subpool")?
> 
> And 832b50725373 ("mm: mmap_lock: use local locks instead of disabling
> preemption")? (the RT people want that...)
> 

This one at least is theoritical in nature for a backport because
PREEMPT_RT cannot be selected as no arch defines ARCH_SUPPORTS_RT
yet. If is was heading to any stable branch, it would be under
https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git/.
The latest kernel there is v5.10-rt and the Fixes tag is for 5.11 so that
fix would be ignored.

-- 
Mel Gorman
SUSE Labs