[PATCH RFC v3 0/7] mm: Fix MF_DELAYED handling on memory failure

[Lisa Wang <wyihan@google.com>]

Here's a third revision to fix MF_DELAYED handling on memory failure.

This patch series addresses an issue in the memory failure handling path
where MF_DELAYED is incorrectly treated as an error. This issue was
discovered while testing memory failure handling for guest_memfd.

The proposed solution involves -
1. Clarifying the definition of MF_DELAYED to mean that memory failure
   handling is only partially completed, and that the metadata for the
   memory that failed (as in struct page/folio) is still referenced.
2. Updating shmem’s handling to align with the clarified definition.
3. Updating how the result of .error_remove_folio() is interpreted.

Changes from v2:
+ Address the comment about fixing the typos and clarifying the
  'unmapped' status from Jiaqi
+ Address the comment about merging shmem memory failure selftest into
  memory failure selftest from Baolin
+ Align the consistent style in truncate_error_folio suggested by Miaohe
+ Fix some bugs found out by Sashiko. e.g. set vcpu register when VM is
  running.
Thanks!

Would like to request reviews from Miaohe and Baolin regarding the
selftests:
+ Is adding more TEST_F()s suitable?
+ Are you expecting refactoring to reduce code duplication in
  selftests?

Would like to get feedback on the direction of selftests before looking
into adding selftests for hugetlb.

Also, hope to get some feedback about the guest memfd test in this
version. At a high level, should I move the memory-failure specific
guest_memfd tests into a new file? guest_memfd_test is starting to get
really large. Also, I'd like to use the kselftest_harness to handle
teardown/cleanup (unpoisoning memory poisoned for testing) on test
failure.

+ RFC v2: https://lore.kernel.org/r/20260319-memory-failure-mf-delayed-fix-rfc-v2-v2-0-92c596402a7a@google.com

Signed-off-by: Lisa Wang <wyihan@google.com>
---
Lisa Wang (7):
      mm: memory_failure: Clarify the MF_DELAYED definition
      mm: memory_failure: Allow truncate_error_folio to return MF_DELAYED
      mm: shmem: Update shmem handler to the MF_DELAYED definition
      mm: memory_failure: Generalize extra_pins handling to all MF_DELAYED cases
      mm: selftests: Add shmem into memory failure test
      KVM: selftests: Add memory failure tests in guest_memfd_test
      KVM: selftests: Test guest_memfd behavior with respect to stage 2 page tables

 mm/memory-failure.c                            |  27 ++-
 mm/shmem.c                                     |   2 +-
 tools/testing/selftests/kvm/guest_memfd_test.c | 238 ++++++++++++++++++++++++-
 tools/testing/selftests/mm/memory-failure.c    | 109 ++++++++++-
 4 files changed, 357 insertions(+), 19 deletions(-)
---
base-commit: 513de28cb70afe6d3e24fe5b432c13363f9cfda6
change-id: 20260403-memory-failure-mf-delayed-fix-rfc-v3-02878d7ef5b5

Best regards,
-- 
Lisa Wang <wyihan@google.com>