Re: [PATCH v1 0/4]mm: convert totalram_pages, totalhigh_pages and managed pages to atomic

From: Arun KS <arunks@codeaurora.org>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: keescook@chromium.org, minchan@kernel.org, getarunks@gmail.com,
	gregkh@linuxfoundation.org, akpm@linux-foundation.org,
	mhocko@kernel.org, vbabka@suse.cz, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, julia.lawall@lip6.fr
Subject: Re: [PATCH v1 0/4]mm: convert totalram_pages, totalhigh_pages and managed pages to atomic
Date: Tue, 06 Nov 2018 14:13:12 +0530	[thread overview]
Message-ID: <22fa2222012341a54f6b0b6aea341aa2@codeaurora.org> (raw)
In-Reply-To: <10c88df6-dbb1-7490-628c-055d59b5ad8e@yandex-team.ru>

On 2018-11-06 14:07, Konstantin Khlebnikov wrote:
> On 06.11.2018 11:30, Arun KS wrote:
>> On 2018-11-06 13:47, Konstantin Khlebnikov wrote:
>>> On 06.11.2018 8:38, Arun KS wrote:
>>>> Any comments?
>>> 
>>> Looks good.
>>> Except unclear motivation behind this change.
>>> This should be in comment of one of patch.
>> 
>> totalram_pages, zone->managed_pages and totalhigh_pages are sometimes 
>> modified outside managed_page_count_lock. Hence convert these variable 
>> to atomic to avoid readers potentially seeing a store tear.
> 
> So, this is just theoretical issue or splat from sanitizer.
> After boot memory online\offline are strictly serialized by 
> rw-semaphore.

Few instances which can race with hot add. Please see below,
https://patchwork.kernel.org/patch/10627521/

Regards,
Arun

> 
>> 
>> Will update the comment.
>> 
>> Regards,
>> Arun
>> 
>>> 
>>> Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>>> 
>>>> 
>>>> Regards,
>>>> Arun
>>>> 
>>>> On 2018-10-26 16:30, Arun KS wrote:
>>>>> This series convert totalram_pages, totalhigh_pages and
>>>>> zone->managed_pages to atomic variables.
>>>>> 
>>>>> The patch was comiple tested on x86(x86_64_defconfig & 
>>>>> i386_defconfig)
>>>>> on tip of linux-mmotm. And memory hotplug tested on arm64, but on 
>>>>> an
>>>>> older version of kernel.
>>>>> 
>>>>> Arun KS (4):
>>>>>   mm: Fix multiple evaluvations of totalram_pages and managed_pages
>>>>>   mm: Convert zone->managed_pages to atomic variable
>>>>>   mm: convert totalram_pages and totalhigh_pages variables to 
>>>>> atomic
>>>>>   mm: Remove managed_page_count spinlock
>>>>> 
>>>>>  arch/csky/mm/init.c                           |  4 +-
>>>>>  arch/powerpc/platforms/pseries/cmm.c          | 10 ++--
>>>>>  arch/s390/mm/init.c                           |  2 +-
>>>>>  arch/um/kernel/mem.c                          |  3 +-
>>>>>  arch/x86/kernel/cpu/microcode/core.c          |  5 +-
>>>>>  drivers/char/agp/backend.c                    |  4 +-
>>>>>  drivers/gpu/drm/amd/amdkfd/kfd_crat.c         |  2 +-
>>>>>  drivers/gpu/drm/i915/i915_gem.c               |  2 +-
>>>>>  drivers/gpu/drm/i915/selftests/i915_gem_gtt.c |  4 +-
>>>>>  drivers/hv/hv_balloon.c                       | 19 +++----
>>>>>  drivers/md/dm-bufio.c                         |  2 +-
>>>>>  drivers/md/dm-crypt.c                         |  2 +-
>>>>>  drivers/md/dm-integrity.c                     |  2 +-
>>>>>  drivers/md/dm-stats.c                         |  2 +-
>>>>>  drivers/media/platform/mtk-vpu/mtk_vpu.c      |  2 +-
>>>>>  drivers/misc/vmw_balloon.c                    |  2 +-
>>>>>  drivers/parisc/ccio-dma.c                     |  4 +-
>>>>>  drivers/parisc/sba_iommu.c                    |  4 +-
>>>>>  drivers/staging/android/ion/ion_system_heap.c |  2 +-
>>>>>  drivers/xen/xen-selfballoon.c                 |  6 +--
>>>>>  fs/ceph/super.h                               |  2 +-
>>>>>  fs/file_table.c                               |  7 +--
>>>>>  fs/fuse/inode.c                               |  2 +-
>>>>>  fs/nfs/write.c                                |  2 +-
>>>>>  fs/nfsd/nfscache.c                            |  2 +-
>>>>>  fs/ntfs/malloc.h                              |  2 +-
>>>>>  fs/proc/base.c                                |  2 +-
>>>>>  include/linux/highmem.h                       | 28 ++++++++++-
>>>>>  include/linux/mm.h                            | 27 +++++++++-
>>>>>  include/linux/mmzone.h                        | 15 +++---
>>>>>  include/linux/swap.h                          |  1 -
>>>>>  kernel/fork.c                                 |  5 +-
>>>>>  kernel/kexec_core.c                           |  5 +-
>>>>>  kernel/power/snapshot.c                       |  2 +-
>>>>>  lib/show_mem.c                                |  2 +-
>>>>>  mm/highmem.c                                  |  4 +-
>>>>>  mm/huge_memory.c                              |  2 +-
>>>>>  mm/kasan/quarantine.c                         |  2 +-
>>>>>  mm/memblock.c                                 |  6 +--
>>>>>  mm/memory_hotplug.c                           |  4 +-
>>>>>  mm/mm_init.c                                  |  2 +-
>>>>>  mm/oom_kill.c                                 |  2 +-
>>>>>  mm/page_alloc.c                               | 71 
>>>>> +++++++++++++--------------
>>>>>  mm/shmem.c                                    |  7 +--
>>>>>  mm/slab.c                                     |  2 +-
>>>>>  mm/swap.c                                     |  2 +-
>>>>>  mm/util.c                                     |  2 +-
>>>>>  mm/vmalloc.c                                  |  4 +-
>>>>>  mm/vmstat.c                                   |  4 +-
>>>>>  mm/workingset.c                               |  2 +-
>>>>>  mm/zswap.c                                    |  4 +-
>>>>>  net/dccp/proto.c                              |  7 +--
>>>>>  net/decnet/dn_route.c                         |  2 +-
>>>>>  net/ipv4/tcp_metrics.c                        |  2 +-
>>>>>  net/netfilter/nf_conntrack_core.c             |  7 +--
>>>>>  net/netfilter/xt_hashlimit.c                  |  5 +-
>>>>>  net/sctp/protocol.c                           |  7 +--
>>>>>  security/integrity/ima/ima_kexec.c            |  2 +-
>>>>>  58 files changed, 195 insertions(+), 144 deletions(-)