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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 17 Jun 2019 16:12:56 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5HFCtCS45154384 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 17 Jun 2019 15:12:55 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 16452A405C; Mon, 17 Jun 2019 15:12:55 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 16509A405B; Mon, 17 Jun 2019 15:12:54 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.8.53]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 17 Jun 2019 15:12:53 +0000 (GMT) Date: Mon, 17 Jun 2019 18:12:52 +0300 From: Mike Rapoport To: Mark Rutland Cc: Qian Cai , Will Deacon , akpm@linux-foundation.org, Roman Gushchin , catalin.marinas@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() References: <1559656836-24940-1-git-send-email-cai@lca.pw> <20190604142338.GC24467@lakrids.cambridge.arm.com> <20190610114326.GF15979@fuggles.cambridge.arm.com> <1560187575.6132.70.camel@lca.pw> <20190611100348.GB26409@lakrids.cambridge.arm.com> <20190613121100.GB25164@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190613121100.GB25164@rapoport-lnx> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19061715-0028-0000-0000-0000037B0CCC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061715-0029-0000-0000-0000243B119D Message-Id: <20190617151252.GF16810@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-17_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=7 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906170136 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 13, 2019 at 03:11:01PM +0300, Mike Rapoport wrote: > On Tue, Jun 11, 2019 at 11:03:49AM +0100, Mark Rutland wrote: > > On Mon, Jun 10, 2019 at 01:26:15PM -0400, Qian Cai wrote: > > > On Mon, 2019-06-10 at 12:43 +0100, Will Deacon wrote: > > > > 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 > > > > > > --- > > > > > >  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()? > > > > > > > > So can I take the above for -rc5, or is somebody else working on a different > > > > fix to implement pgd_alloc_kernel()? > > > > > > The offensive commit "arm64: switch to generic version of pte allocation" is not > > > yet in the mainline, but only in the Andrew's tree and linux-next, and I doubt > > > Andrew will push this out any time sooner given it is broken. > > > > I'd assumed that Mike would respin these patches to implement and use > > pgd_alloc_kernel() (or take gfp flags) and the updated patches would > > replace these in akpm's tree. > > > > Mike, could you confirm what your plan is? I'm happy to review/test > > updated patches for arm64. > > The log Qian Cai posted at [1] and partially cited below confirms that the > failure happens when *user* PGDs are allocated and the addition of > __GFP_ACCOUNT to gfp flags used by pgd_alloc() only uncovered another > issue. Indeed the accounting of the PGD memory uncovered a dangling pointer to pgd_cache :) The pgd_cache was initialized twice and it made memcg and slub sysfs go nuts. To be frank, I've got lost in their cross-initialization, cross-referencing and update sequences, but for sure extra initialization of pgd_cache was bogus. I've double checked the 'if (mm == &init_mm)' and it's not needed. The EFI PGD is allocated before memcg is up and other kernel allocations of pgd (if we'll have any) would be bypassed by memcg_kmem_bypass(). 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 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 Signed-off-by: Mike Rapoport --- arch/arm64/include/asm/pgtable.h | 3 +-- arch/arm64/mm/pgd.c | 5 +---- 2 files changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 3191b9f..c7a802d 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -851,8 +851,7 @@ extern int kern_addr_valid(unsigned long addr); #include -void pgd_cache_init(void); -#define pgtable_cache_init pgd_cache_init +static inline void pgtable_cache_init(void) { } /* * On AArch64, the cache coherency is handled via the set_pte_at() function. diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c index 53c48f5..3f0a744 100644 --- a/arch/arm64/mm/pgd.c +++ b/arch/arm64/mm/pgd.c @@ -32,13 +32,10 @@ pgd_t *pgd_alloc(struct mm_struct *mm) { gfp_t gfp = GFP_PGTABLE_USER; - if (unlikely(mm == &init_mm)) - gfp = GFP_PGTABLE_KERNEL; - if (PGD_SIZE == PAGE_SIZE) return (pgd_t *)__get_free_page(gfp); else - return kmem_cache_alloc(pgd_cache, GFP_PGTABLE_KERNEL); + return kmem_cache_alloc(pgd_cache, gfp); } void pgd_free(struct mm_struct *mm, pgd_t *pgd) -- 2.7.4 > [1] https://cailca.github.io/files/dmesg.txt > > -- > Sincerely yours, > Mike. > -- Sincerely yours, Mike.