[PATCH v12 0/7] add hugetlb_optimize_vmemmap sysctl

[Muchun Song <songmuchun@bytedance.com>]

This series is based on next-20220428.

This series amis to add hugetlb_optimize_vmemmap sysctl to enable or disable
the feature of optimizing vmemmap pages associated with HugeTLB pages.

v12:
  - Add patch 3 and patch 4 to handle the coexistence of hugetlb_free_vmemmap
    and memory_hotplug.memmap_on_memory (David).
  - Remove Reviewed-by from Mike in the last parch since it is changed.

v11:
  - Collect Reviewed-by from Mike.
  - Remove hugetlb_optimize_vmemmap_enabled() check from flush_free_hpage_work().

v10:
  - Collect Reviewed-by from Mike.
  - Remove hugetlb_optimize_vmemmap_enabled() check from
    hugetlb_optimize_vmemmap_pages() (Mike).
  - Add more explanation to Documentation/admin-guide/sysctl/vm.rst.
  - Fix cannot disable the feature via hugetlb_optimize_vmemmap sysctl (Mike).
  - Update patch 2's commit log (Mike).

v9:
  - Go back to v3 since checking the size of struct page at config time is
    very complex.

v8:
  - Fix compilation (scripts/selinux/mdp/mdp.c) error when
    CONFIG_SECURITY_SELINUX is selected.

v7:
  - Fix circular dependency issue reported by kernel test robot.
  - Introduce CONFIG_HUGETLB_PAGE_HAS_OPTIMIZE_VMEMMAP instead of
    STRUCT_PAGE_SIZE_IS_POWER_OF_2.
  - Add more comments into vm.rst to explain hugetlb_optimize_vmemmap (Andrew).
  - Drop the patch "sysctl: allow to set extra1 to SYSCTL_ONE".
  - Add a new patch "use kstrtobool for hugetlb_vmemmap param parsing".
  - Reuse static_key's refcount to count the number of HugeTLB pages with
    vmemmap pages optimized to simplify the lock scheme.

v6:
  - Remove "make syncconfig" from Kbuild.

v5:
  - Fix not working properly if one is workig off of a very clean build
    reported by Luis Chamberlain.
  - Add Suggested-by for Luis Chamberlain.

v4:
  - Introduce STRUCT_PAGE_SIZE_IS_POWER_OF_2 inspired by Luis.

v3:
  - Add pr_warn_once() (Mike).
  - Handle the transition from enabling to disabling (Luis)

v2:
  - Fix compilation when !CONFIG_MHP_MEMMAP_ON_MEMORY reported by kernel
    test robot <lkp@intel.com>.
  - Move sysctl code from kernel/sysctl.c to mm/hugetlb_vmemmap.c.

Muchun Song (7):
  mm: hugetlb_vmemmap: disable hugetlb_optimize_vmemmap when struct page
    crosses page boundaries
  mm: hugetlb_vmemmap: use kstrtobool for hugetlb_vmemmap param parsing
  mm: memory_hotplug: enumerate all supported section flags
  mm: hotplug: introduce SECTION_CANNOT_OPTIMIZE_VMEMMAP
  mm: hugetlb_vmemmap: remove hugetlb_optimize_vmemmap_enabled()
  sysctl: handle table->maxlen properly for proc_dobool
  mm: hugetlb_vmemmap: add hugetlb_optimize_vmemmap sysctl

 Documentation/admin-guide/kernel-parameters.txt | 22 +++----
 Documentation/admin-guide/sysctl/vm.rst         | 38 ++++++++++++
 arch/arm64/mm/flush.c                           | 13 +---
 fs/lockd/svc.c                                  |  2 +-
 include/linux/kconfig.h                         |  1 +
 include/linux/mmzone.h                          | 54 +++++++++++++---
 include/linux/page-flags.h                      | 16 +----
 kernel/sysctl.c                                 | 22 ++++---
 mm/hugetlb_vmemmap.c                            | 82 ++++++++++++++++++-------
 mm/memory_hotplug.c                             |  7 ++-
 mm/sparse.c                                     |  7 +++
 11 files changed, 186 insertions(+), 78 deletions(-)

-- 
2.11.0