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Message-ID: <3c25ec6f-cd33-9445-a76f-6ec2c30755f5@redhat.com>
Date:   Wed, 27 Sep 2023 19:11:37 +0200
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Subject: Re: [PATCH 00/10] Fix confusion around MAX_ORDER
Content-Language: en-US
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
        David Hildenbrand <david@redhat.com>, quic_jhugo@quicinc.com,
        snitzer@kernel.org, dm <dm-devel@redhat.com>,
        Mikulas Patocka <mpatocka@redhat.com>
Cc:     linux-mm@kvack.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20230315113133.11326-1-kirill.shutemov@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <20230315113133.11326-1-kirill.shutemov@linux.intel.com>
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On 3/15/23 12:31, Kirill A. Shutemov wrote:
> MAX_ORDER currently defined as number of orders page allocator supports:
> user can ask buddy allocator for page order between 0 and MAX_ORDER-1.
> 
> This definition is counter-intuitive and lead to number of bugs all over
> the kernel.
> 
> Fix the bugs and then change the definition of MAX_ORDER to be
> inclusive: the range of orders user can ask from buddy allocator is
> 0..MAX_ORDER now.

Looks like this crossed with three changes that introduced new
uses of MAX_ORDER:

drivers/accel/qaic/qaic_data.c:         max_order = min(MAX_ORDER - 1, get_order(size));
drivers/md/dm-crypt.c:  unsigned int order = MAX_ORDER - 1;
drivers/md/dm-flakey.c: order = MAX_ORDER - 1;

The bugs are all benign, MAX_ORDER - 1 can simply be changed
to MAX_ORDER to be consistent with the new world order.

CCing relevant maintainers...

Paolo

> Kirill A. Shutemov (10):
>    sparc/mm: Fix MAX_ORDER usage in tsb_grow()
>    um: Fix MAX_ORDER usage in linux_main()
>    floppy: Fix MAX_ORDER usage
>    drm/i915: Fix MAX_ORDER usage in i915_gem_object_get_pages_internal()
>    genwqe: Fix MAX_ORDER usage
>    perf/core: Fix MAX_ORDER usage in rb_alloc_aux_page()
>    mm/page_reporting: Fix MAX_ORDER usage in page_reporting_register()
>    mm/slub: Fix MAX_ORDER usage in calculate_order()
>    iommu: Fix MAX_ORDER usage in __iommu_dma_alloc_pages()
>    mm, treewide: Redefine MAX_ORDER sanely
> 
>   .../admin-guide/kdump/vmcoreinfo.rst          |  2 +-
>   .../admin-guide/kernel-parameters.txt         |  2 +-
>   arch/arc/Kconfig                              |  4 +-
>   arch/arm/Kconfig                              |  9 ++---
>   arch/arm/configs/imx_v6_v7_defconfig          |  2 +-
>   arch/arm/configs/milbeaut_m10v_defconfig      |  2 +-
>   arch/arm/configs/oxnas_v6_defconfig           |  2 +-
>   arch/arm/configs/pxa_defconfig                |  2 +-
>   arch/arm/configs/sama7_defconfig              |  2 +-
>   arch/arm/configs/sp7021_defconfig             |  2 +-
>   arch/arm64/Kconfig                            | 27 ++++++-------
>   arch/arm64/include/asm/sparsemem.h            |  2 +-
>   arch/arm64/kvm/hyp/include/nvhe/gfp.h         |  2 +-
>   arch/arm64/kvm/hyp/nvhe/page_alloc.c          | 10 ++---
>   arch/csky/Kconfig                             |  2 +-
>   arch/ia64/Kconfig                             |  8 ++--
>   arch/ia64/include/asm/sparsemem.h             |  4 +-
>   arch/ia64/mm/hugetlbpage.c                    |  2 +-
>   arch/loongarch/Kconfig                        | 15 +++-----
>   arch/m68k/Kconfig.cpu                         |  5 +--
>   arch/mips/Kconfig                             | 19 ++++------
>   arch/nios2/Kconfig                            |  7 +---
>   arch/powerpc/Kconfig                          | 27 ++++++-------
>   arch/powerpc/configs/85xx/ge_imp3a_defconfig  |  2 +-
>   arch/powerpc/configs/fsl-emb-nonhw.config     |  2 +-
>   arch/powerpc/mm/book3s64/iommu_api.c          |  2 +-
>   arch/powerpc/mm/hugetlbpage.c                 |  2 +-
>   arch/powerpc/platforms/powernv/pci-ioda.c     |  2 +-
>   arch/sh/configs/ecovec24_defconfig            |  2 +-
>   arch/sh/mm/Kconfig                            | 17 ++++-----
>   arch/sparc/Kconfig                            |  5 +--
>   arch/sparc/kernel/pci_sun4v.c                 |  2 +-
>   arch/sparc/kernel/traps_64.c                  |  2 +-
>   arch/sparc/mm/tsb.c                           |  4 +-
>   arch/xtensa/Kconfig                           |  5 +--
>   drivers/base/regmap/regmap-debugfs.c          |  8 ++--
>   drivers/block/floppy.c                        |  2 +-
>   drivers/crypto/ccp/sev-dev.c                  |  2 +-
>   drivers/crypto/hisilicon/sgl.c                |  6 +--
>   .../gpu/drm/i915/gem/selftests/huge_pages.c   |  2 +-
>   drivers/gpu/drm/ttm/ttm_pool.c                | 22 +++++------
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  2 +-
>   drivers/iommu/dma-iommu.c                     |  4 +-
>   drivers/irqchip/irq-gic-v3-its.c              |  4 +-
>   drivers/md/dm-bufio.c                         |  2 +-
>   drivers/misc/genwqe/card_utils.c              |  2 +-
>   .../net/ethernet/hisilicon/hns3/hns3_enet.c   |  2 +-
>   drivers/net/ethernet/ibm/ibmvnic.h            |  2 +-
>   drivers/video/fbdev/hyperv_fb.c               |  4 +-
>   drivers/video/fbdev/vermilion/vermilion.c     |  2 +-
>   drivers/virtio/virtio_balloon.c               |  2 +-
>   drivers/virtio/virtio_mem.c                   | 12 +++---
>   fs/ramfs/file-nommu.c                         |  2 +-
>   include/drm/ttm/ttm_pool.h                    |  2 +-
>   include/linux/hugetlb.h                       |  2 +-
>   include/linux/mmzone.h                        | 10 ++---
>   include/linux/pageblock-flags.h               |  4 +-
>   include/linux/slab.h                          |  6 +--
>   kernel/crash_core.c                           |  2 +-
>   kernel/dma/pool.c                             |  6 +--
>   mm/Kconfig                                    |  6 +--
>   mm/compaction.c                               |  8 ++--
>   mm/debug_vm_pgtable.c                         |  4 +-
>   mm/huge_memory.c                              |  2 +-
>   mm/hugetlb.c                                  |  4 +-
>   mm/kmsan/init.c                               |  6 +--
>   mm/memblock.c                                 |  2 +-
>   mm/memory_hotplug.c                           |  4 +-
>   mm/page_alloc.c                               | 38 +++++++++----------
>   mm/page_isolation.c                           | 12 +++---
>   mm/page_owner.c                               |  6 +--
>   mm/page_reporting.c                           |  4 +-
>   mm/shuffle.h                                  |  2 +-
>   mm/slab.c                                     |  2 +-
>   mm/slub.c                                     |  4 +-
>   mm/vmscan.c                                   |  2 +-
>   mm/vmstat.c                                   | 14 +++----
>   net/smc/smc_ib.c                              |  2 +-
>   security/integrity/ima/ima_crypto.c           |  2 +-
>   tools/testing/memblock/linux/mmzone.h         |  6 +--
>   80 files changed, 210 insertions(+), 240 deletions(-)
>