[PATCH v4 0/5] Enhance soft hwpoison handling and injection

[Jane Chu]

Changes in v4:
  - collected R-B from Oscar Salvador
  - collected Acked-by from Miaohe Lin
  - fixed comment on MF_DELAYED, and comments for better coding. - Miaohe Lin
 
Changes in v3:
  - rebased to mainline as of 5/20/2024
  - added an acked-by from Miaohe Lin
  - picked up a R-B from Oscar Salvador
  - fixed/clarified comments about MF_IGNORED/MF_FAILED definition and
    usage. - Oscar Salvador
  - invoke hwpoison_filter slightly earlier to avoid unnecessary THP split,
    and with refcount held. - Miaohe Lin
  - added comments to try_to_split_thp_page() on when not to release page
    refcount.  - Oscar Salvador
  - added action_result() in a couple cases, but take care not to overwrite
    the intended returns.  - Oscar Salvador

Changes in v2:
  - rebased to mm-stable as of 5/8/2024
  - added RB by Oscar Salvador
  - comments from Oscar on patch 1-of-3: clarify changelog
  - comments from Miahe Lin on patch 3-of-3: remove unnecessary user page
    checking and remove incorrect put_page() in kill_procs_now().
    Invoke kill_procs_now() regardless MF_ACTIN_REQUIRED is set or not,
    moved hwpoison_filter() higher up.
  - added two patches 3-of-5 and 4-of-5

This series aim at the following enhancement -
- Let one hwpoison injector, that is, madvise(MADV_HWPOISON) to behave
  more like as if a real UE occurred. Because the other two injectors
  such as hwpoison-inject and the 'einj' on x86 can't, and it seems to
  me we need a better simulation to real UE scenario.
- For years, if the kernel is unable to unmap a hwpoisoned page, it send
  a SIGKILL instead of SIGBUS to prevent user process from potentially
  accessing the page again. But in doing so, the user process also lose
  important information: vaddr, for recovery.  Fortunately, the kernel
  already has code to kill process re-accessing a hwpoisoned page, so
  remove the '!unmap_success' check.
- Right now, if a thp page under GUP longterm pin is hwpoisoned, and
  kernel cannot split the thp page, memory-failure simply ignores
  the UE and returns.  That's not ideal, it could deliver a SIGBUS with
  useful information for userspace recovery.


Jane Chu (5):
  mm/memory-failure: try to send SIGBUS even if unmap failed
  mm/madvise: Add MF_ACTION_REQUIRED to madvise(MADV_HWPOISON)
  mm/memory-failure: improve memory failure action_result messages
  mm/memory-failure: move hwpoison_filter() higher up
  mm/memory-failure: send SIGBUS in the event of thp split fail

 include/linux/mm.h      |   2 +
 include/ras/ras_event.h |   2 +
 mm/madvise.c            |   2 +-
 mm/memory-failure.c     | 106 +++++++++++++++++++++++++++++-----------
 4 files changed, 82 insertions(+), 30 deletions(-)

-- 
2.39.3