[PATCH v4 0/7] mm: Fix MF_DELAYED handling on memory failure

[Lisa Wang <wyihan@google.com>]

Here's a fourth 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 v3:
+ Split an independent guest_memfd_memory_failure_test, as suggested by
  Ackerley and Sean
+ Align error logging style in truncate_error_folio, as suggested by
  Miaohe and David
+ Verify a clean shmem page can be read successfully after soft-offline
  memory failure, as suggested by Miaohe
Thanks!

+ RFC v3: https://lore.kernel.org/all/20260408-memory-failure-mf-delayed-fix-rfc-v3-v3-0-718f45eb7c75@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 the guest_memfd memory failure test
      KVM: selftests: Test guest_memfd behavior with respect to stage 2 page tables

 mm/memory-failure.c                                |  29 +-
 mm/shmem.c                                         |   2 +-
 tools/testing/selftests/kvm/Makefile.kvm           |   2 +
 .../kvm/guest_memfd_memory_failure_test.c          | 402 +++++++++++++++++++++
 tools/testing/selftests/mm/memory-failure.c        | 111 +++++-
 5 files changed, 527 insertions(+), 19 deletions(-)
---
base-commit: 38741a8e3bc1b809d64f8c8885ab15c3e40700ff
change-id: 20260527-memory-failure-mf-delayed-fix-7d5a8f4a8a8b

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