linux-kernel - Re: [PATCH -next] arm64/mm: fix a bogus GFP flag in pgd

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Message-ID: <20190618065414.GA15875@brain-police>
Date:   Tue, 18 Jun 2019 07:54:15 +0100
From:   Will Deacon <will@...nel.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>, Qian Cai <cai@....pw>,
        akpm@...ux-foundation.org, Roman Gushchin <guro@...com>,
        catalin.marinas@....com, linux-kernel@...r.kernel.org,
        mhocko@...nel.org, linux-mm@...ck.org, vdavydov.dev@...il.com,
        hannes@...xchg.org, cgroups@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH -next] arm64/mm: fix a bogus GFP flag in pgd_alloc()

On Tue, Jun 18, 2019 at 09:12:59AM +0300, Mike Rapoport wrote:
> On Mon, Jun 17, 2019 at 05:36:30PM +0100, Will Deacon wrote:
> > On Mon, Jun 17, 2019 at 06:12:52PM +0300, Mike Rapoport wrote:
> > > Andrew, can you please add the patch below as an incremental fix?
> > > 
> > > With this the arm64::pgd_alloc() should be in the right shape.
> > > 
> > > 
> > > From 1c1ef0bc04c655689c6c527bd03b140251399d87 Mon Sep 17 00:00:00 2001
> > > From: Mike Rapoport <rppt@...ux.ibm.com>
> > > Date: Mon, 17 Jun 2019 17:37:43 +0300
> > > Subject: [PATCH] arm64/mm: don't initialize pgd_cache twice
> > > 
> > > When PGD_SIZE != PAGE_SIZE, arm64 uses kmem_cache for allocation of PGD
> > > memory. That cache was initialized twice: first through
> > > pgtable_cache_init() alias and then as an override for weak
> > > pgd_cache_init().
> > > 
> > > After enabling accounting for the PGD memory, this created a confusion for
> > > memcg and slub sysfs code which resulted in the following errors:
> > > 
> > > [   90.608597] kobject_add_internal failed for pgd_cache(13:init.scope) (error: -2 parent: cgroup)
> > > [   90.678007] kobject_add_internal failed for pgd_cache(13:init.scope) (error: -2 parent: cgroup)
> > > [   90.713260] kobject_add_internal failed for pgd_cache(21:systemd-tmpfiles-setup.service) (error: -2 parent: cgroup)
> > > 
> > > Removing the alias from pgtable_cache_init() and keeping the only pgd_cache
> > > initialization in pgd_cache_init() resolves the problem and allows
> > > accounting of PGD memory.
> > > 
> > > Reported-by: Qian Cai <cai@....pw>
> > > Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> > > ---
> > >  arch/arm64/include/asm/pgtable.h | 3 +--
> > >  arch/arm64/mm/pgd.c              | 5 +----
> > >  2 files changed, 2 insertions(+), 6 deletions(-)
> > 
> > Looks like this actually fixes caa841360134 ("x86/mm: Initialize PGD cache
> > during mm initialization") due to an unlucky naming conflict!
> > 
> > In which case, I'd actually prefer to take this fix asap via the arm64
> > tree. Is that ok?
> 
> I suppose so, it just won't apply as is. Would you like a patch against the
> current upstream?

Yes, please. I'm assuming it's a straightforward change (please shout if it
isn't).

Will