Linux-ARM-Kernel Archive on lore.kernel.org
 help / color / Atom feed
From: Mark Rutland <mark.rutland@arm.com>
To: Qian Cai <cai@lca.pw>, rppt@linux.ibm.com
Cc: 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, akpm@linux-foundation.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 15:23:38 +0100
Message-ID: <20190604142338.GC24467@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <1559656836-24940-1-git-send-email-cai@lca.pw>

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.

Do we need a separate pgd_alloc_kernel()?

Thanks,
Mark.

[1] https://lkml.kernel.org/r/20190505061956.GE15755@rapoport-lnx

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-04 14:00 Qian Cai
2019-06-04 14:23 ` Mark Rutland [this message]
2019-06-04 14:30   ` Mark Rutland
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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190604142338.GC24467@lakrids.cambridge.arm.com \
    --to=mark.rutland@arm.com \
    --cc=akpm@linux-foundation.org \
    --cc=cai@lca.pw \
    --cc=catalin.marinas@arm.com \
    --cc=cgroups@vger.kernel.org \
    --cc=hannes@cmpxchg.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=rppt@linux.ibm.com \
    --cc=vdavydov.dev@gmail.com \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-ARM-Kernel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/0 linux-arm-kernel/git/0.git
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/1 linux-arm-kernel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arm-kernel linux-arm-kernel/ https://lore.kernel.org/linux-arm-kernel \
		linux-arm-kernel@lists.infradead.org infradead-linux-arm-kernel@archiver.kernel.org
	public-inbox-index linux-arm-kernel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-arm-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox