[PATCH v3 0/4] add hugetlb_free_vmemmap sysctl

[Muchun Song]

This series amis to add hugetlb_free_vmemmap sysctl to enable the feature
of freeing vmemmap pages of HugeTLB pages.

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@xxxxxxxxx>.
  - Move sysctl code from kernel/sysctl.c to mm/hugetlb_vmemmap.c.

Muchun Song (4):
  mm: hugetlb: disable freeing vmemmap pages when struct page crosses
    page boundaries
  mm: memory_hotplug: override memmap_on_memory when
    hugetlb_free_vmemmap=on
  sysctl: allow to set extra1 to SYSCTL_ONE
  mm: hugetlb: add hugetlb_free_vmemmap sysctl

 Documentation/admin-guide/sysctl/vm.rst |  14 ++++
 include/linux/memory_hotplug.h          |   9 +++
 kernel/sysctl.c                         |   2 +-
 mm/hugetlb_vmemmap.c                    | 113 +++++++++++++++++++++++++++-----
 mm/hugetlb_vmemmap.h                    |   4 +-
 mm/memory_hotplug.c                     |  27 ++++++--
 6 files changed, 143 insertions(+), 26 deletions(-)

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2.11.0