[PATCH v5 00/25] mm: Page fault accounting cleanups

[Peter Xu <peterx@redhat.com>]

v5:
- rebase to linux-next/akpm, add r-bs
- patch 1: pass vm_fault_t into mm_account_fault() [DavidR]
- patch 25: fix comment in get_user_pages() to remove the ref to task [John]
- dropped the unicore32 patch because the arch was thrown away

This is v5 of the pf accounting cleanup series.  It originates from Gerald
Schaefer's report on an issue a week ago regarding to incorrect page fault
accountings for retried page fault after commit 4064b9827063 ("mm: allow
VM_FAULT_RETRY for multiple times"):

  https://lore.kernel.org/lkml/20200610174811.44b94525@thinkpad/

What this series did:

  - Correct page fault accounting: we do accounting for a page fault (no matter
    whether it's from #PF handling, or gup, or anything else) only with the one
    that completed the fault.  For example, page fault retries should not be
    counted in page fault counters.  Same to the perf events.

  - Unify definition of PERF_COUNT_SW_PAGE_FAULTS: currently this perf event is
    used in an adhoc way across different archs.

    Case (1): for many archs it's done at the entry of a page fault handler, so
    that it will also cover e.g. errornous faults.

    Case (2): for some other archs, it is only accounted when the page fault is
    resolved successfully.

    Case (3): there're still quite some archs that have not enabled this perf event.

    Since this series will touch merely all the archs, we unify this perf event
    to always follow case (1), which is the one that makes most sense.  And
    since we moved the accounting into handle_mm_fault, the other two MAJ/MIN
    perf events are well taken care of naturally.

  - Unify definition of "major faults": the definition of "major fault" is
    slightly changed when used in accounting (not VM_FAULT_MAJOR).  More
    information in patch 1.

  - Always account the page fault onto the one that triggered the page fault.
    This does not matter much for #PF handlings, but mostly for gup.  More
    information on this in patch 25.

Patchset layout:

Patch 1:     Introduced the accounting in handle_mm_fault(), not enabled.
Patch 2-23:  Enable the new accounting for arch #PF handlers one by one.
Patch 24:    Enable the new accounting for the rest outliers (gup, iommu, etc.)
Patch 25:    Cleanup GUP task_struct pointer since it's not needed any more

For each of the patch that fixes a specific arch, I'm CCing the maintainers and
the arch list if there is.  Besides, I only lightly tested this series on x86.

Please have a look, thanks.

Peter Xu (25):
  mm: Do page fault accounting in handle_mm_fault
  mm/alpha: Use general page fault accounting
  mm/arc: Use general page fault accounting
  mm/arm: Use general page fault accounting
  mm/arm64: Use general page fault accounting
  mm/csky: Use general page fault accounting
  mm/hexagon: Use general page fault accounting
  mm/ia64: Use general page fault accounting
  mm/m68k: Use general page fault accounting
  mm/microblaze: Use general page fault accounting
  mm/mips: Use general page fault accounting
  mm/nds32: Use general page fault accounting
  mm/nios2: Use general page fault accounting
  mm/openrisc: Use general page fault accounting
  mm/parisc: Use general page fault accounting
  mm/powerpc: Use general page fault accounting
  mm/riscv: Use general page fault accounting
  mm/s390: Use general page fault accounting
  mm/sh: Use general page fault accounting
  mm/sparc32: Use general page fault accounting
  mm/sparc64: Use general page fault accounting
  mm/x86: Use general page fault accounting
  mm/xtensa: Use general page fault accounting
  mm: Clean up the last pieces of page fault accountings
  mm/gup: Remove task_struct pointer for all gup code

 arch/alpha/mm/fault.c                       |   8 +-
 arch/arc/kernel/process.c                   |   2 +-
 arch/arc/mm/fault.c                         |  18 +--
 arch/arm/mm/fault.c                         |  25 +----
 arch/arm64/mm/fault.c                       |  29 +----
 arch/csky/mm/fault.c                        |  13 +--
 arch/hexagon/mm/vm_fault.c                  |   9 +-
 arch/ia64/mm/fault.c                        |   9 +-
 arch/m68k/mm/fault.c                        |  14 +--
 arch/microblaze/mm/fault.c                  |   9 +-
 arch/mips/mm/fault.c                        |  14 +--
 arch/nds32/mm/fault.c                       |  19 +---
 arch/nios2/mm/fault.c                       |  14 +--
 arch/openrisc/mm/fault.c                    |   9 +-
 arch/parisc/mm/fault.c                      |   8 +-
 arch/powerpc/mm/copro_fault.c               |   7 +-
 arch/powerpc/mm/fault.c                     |  11 +-
 arch/riscv/mm/fault.c                       |  16 +--
 arch/s390/kvm/interrupt.c                   |   2 +-
 arch/s390/kvm/kvm-s390.c                    |   2 +-
 arch/s390/kvm/priv.c                        |   8 +-
 arch/s390/mm/fault.c                        |  16 +--
 arch/s390/mm/gmap.c                         |   4 +-
 arch/sh/mm/fault.c                          |  11 +-
 arch/sparc/mm/fault_32.c                    |  13 +--
 arch/sparc/mm/fault_64.c                    |  11 +-
 arch/um/kernel/trap.c                       |   6 +-
 arch/x86/mm/fault.c                         |  17 +--
 arch/xtensa/mm/fault.c                      |  15 +--
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |   2 +-
 drivers/infiniband/core/umem_odp.c          |   2 +-
 drivers/iommu/amd/iommu_v2.c                |   2 +-
 drivers/iommu/intel/svm.c                   |   3 +-
 drivers/vfio/vfio_iommu_type1.c             |   4 +-
 fs/exec.c                                   |   2 +-
 include/linux/mm.h                          |  16 +--
 kernel/events/uprobes.c                     |   6 +-
 kernel/futex.c                              |   2 +-
 mm/gup.c                                    | 118 ++++++++------------
 mm/hmm.c                                    |   3 +-
 mm/ksm.c                                    |   3 +-
 mm/memory.c                                 |  69 +++++++++++-
 mm/process_vm_access.c                      |   2 +-
 security/tomoyo/domain.c                    |   2 +-
 virt/kvm/async_pf.c                         |   2 +-
 virt/kvm/kvm_main.c                         |   2 +-
 46 files changed, 219 insertions(+), 360 deletions(-)

-- 
2.26.2