[resend to correct the mailing list address] Hello,
This patch series addresses an issue in the memory failure handling path where MF_DELAYED is incorrectly treated as an error. This issue was revealed because guest_memfd’s .error_remove_folio() callback returns MF_DELAYED. Currently, when the .error_remove_folio() callback for guest_memfd returns MF_DELAYED, there are a few issues. 1. truncate_error_folio() maps this to MF_FAILED. This causes memory_failure() to return -EBUSY, which unconditionally triggers a SIGBUS. The process’ configured memory corruption kill policy is ignored - even if PR_MCE_KILL_LATE is set, the process will still get a SIGBUS on deferred memory failures. 2. “Failed to punch page” is printed, even though MF_DELAYED indicates that it was intentionally not punched. The first patch corrects this by updating truncate_error_folio() to propagate MF_DELAYED to its caller. This allows memory_failure() to return 0, indicating success, and lets the delayed handling proceed as designed. This patch also updates me_pagecache_clean() to account for the folio's refcount, which remains elevated during delayed handling, aligning its logic with me_swapcache_dirty(). The subsequent two patches add KVM selftests to validate the fix and the expected behavior of guest_memfd memory failure: The first test patch verifies that memory_failure() now returns 0 in the delayed case and confirms that SIGBUS signaling logic remains correct for other scenarios (e.g., madvise injection or PR_MCE_KILL_EARLY). The second test patch confirms that after a memory failure, the poisoned page is correctly unmapped from the KVM guest's stage 2 page tables and that a subsequent access by the guest correctly notifies the userspace VMM with EHWPOISON. This patch series is built upon kvm/next. In addition, to align with the change of INIT_SHARED and to use the macro wrapper in guest_memfd selftests, we put these patches behind Sean’s patches [1]. For ease of testing, this series is also available, stitched together, at https://github.com/googleprodkernel/linux-cc/tree/memory-failure-mf-delayed-fix-rfc-v1 [1]: https://lore.kernel.org/all/[email protected]/T/ Thank you, Lisa Wang (3): mm: memory_failure: Fix MF_DELAYED handling on truncation during failure 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 | 24 +- .../testing/selftests/kvm/guest_memfd_test.c | 233 ++++++++++++++++++ 2 files changed, 248 insertions(+), 9 deletions(-) -- 2.51.0.788.g6d19910ace-goog
