From: Mark Rutland <mark.rutland@arm.com>
To: Qian Cai <cai@lca.pw>, rppt@linux.ibm.com
Cc: akpm@linux-foundation.org, catalin.marinas@arm.com,
will.deacon@arm.com, linux-kernel@vger.kernel.org,
mhocko@kernel.org, linux-mm@kvack.org, vdavydov.dev@gmail.com,
hannes@cmpxchg.org, cgroups@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH -next] arm64/mm: fix a bogus GFP flag in pgd_alloc()
Date: Tue, 4 Jun 2019 15:30:20 +0100 [thread overview]
Message-ID: <20190604143020.GD24467@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20190604142338.GC24467@lakrids.cambridge.arm.com>
On Tue, Jun 04, 2019 at 03:23:38PM +0100, Mark Rutland wrote:
> On Tue, Jun 04, 2019 at 10:00:36AM -0400, Qian Cai wrote:
> > The commit "arm64: switch to generic version of pte allocation"
> > introduced endless failures during boot like,
> >
> > kobject_add_internal failed for pgd_cache(285:chronyd.service) (error:
> > -2 parent: cgroup)
> >
> > It turns out __GFP_ACCOUNT is passed to kernel page table allocations
> > and then later memcg finds out those don't belong to any cgroup.
>
> Mike, I understood from [1] that this wasn't expected to be a problem,
> as the accounting should bypass kernel threads.
>
> Was that assumption wrong, or is something different happening here?
>
> > backtrace:
> > kobject_add_internal
> > kobject_init_and_add
> > sysfs_slab_add+0x1a8
> > __kmem_cache_create
> > create_cache
> > memcg_create_kmem_cache
> > memcg_kmem_cache_create_func
> > process_one_work
> > worker_thread
> > kthread
> >
> > Signed-off-by: Qian Cai <cai@lca.pw>
> > ---
> > arch/arm64/mm/pgd.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c
> > index 769516cb6677..53c48f5c8765 100644
> > --- a/arch/arm64/mm/pgd.c
> > +++ b/arch/arm64/mm/pgd.c
> > @@ -38,7 +38,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
> > if (PGD_SIZE == PAGE_SIZE)
> > return (pgd_t *)__get_free_page(gfp);
> > else
> > - return kmem_cache_alloc(pgd_cache, gfp);
> > + return kmem_cache_alloc(pgd_cache, GFP_PGTABLE_KERNEL);
>
> This is used to allocate PGDs for both user and kernel pagetables (e.g.
> for the efi runtime services), so while this may fix the regression, I'm
> not sure it's the right fix.
I see that since [1], pgd_alloc() was updated to special-case the
init_mm, which is not sufficient for cases like:
efi_mm.pgd = pgd_alloc(&efi_mm)
... which occurs in a kthread.
So let's have a pgd_alloc_kernel() to make that explicit.
Thanks,
Mark.
next prev parent reply other threads:[~2019-06-04 14:30 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-04 14:00 [PATCH -next] arm64/mm: fix a bogus GFP flag in pgd_alloc() Qian Cai
2019-06-04 14:23 ` Mark Rutland
2019-06-04 14:30 ` Mark Rutland [this message]
2019-06-05 21:33 ` Mike Rapoport
2019-06-04 14:54 ` Mike Rapoport
2019-06-10 11:43 ` Will Deacon
2019-06-10 17:26 ` Qian Cai
2019-06-11 10:03 ` Mark Rutland
2019-06-11 12:41 ` Mike Rapoport
2019-06-11 12:46 ` Qian Cai
2019-06-12 6:57 ` Mike Rapoport
2019-06-12 18:35 ` Qian Cai
2019-06-11 13:02 ` Mark Rutland
2019-06-13 12:11 ` Mike Rapoport
2019-06-13 13:22 ` Qian Cai
2019-06-13 19:44 ` Mike Rapoport
2019-06-17 15:12 ` Mike Rapoport
2019-06-17 16:36 ` Will Deacon
2019-06-18 6:12 ` Mike Rapoport
2019-06-18 6:54 ` Will Deacon
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