[v3,0/5] mm: migrate: support poison recover from migrate folio

Message

Kefeng Wang May 28, 2024, 1:45 p.m. UTC

The folio migration is widely used in kernel, memory compaction, memory
hotplug, soft offline page, numa balance, memory demote/promotion, etc,
but once access a poisoned source folio when migrating, the kernel will
panic.

There is a mechanism in the kernel to recover from uncorrectable memory
errors, ARCH_HAS_COPY_MC(eg, Machine Check Safe Memory Copy on x86), which
is already used in NVDIMM or core-mm paths(eg, CoW, khugepaged, coredump,
ksm copy), see copy_mc_to_{user,kernel}, copy_mc_{user_}highpage callers.

This series of patches provide the recovery mechanism from folio copy for
the widely used folio migration. Please note, because folio migration is
no guarantee of success, so we could chose to make folio migration tolerant
of memory failures, adding folio_mc_copy() which is a #MC versions of
folio_copy(), once accessing a poisoned source folio, we could return error
and make the folio migration fail, and this could avoid the similar panic
shown below.

  CPU: 1 PID: 88343 Comm: test_softofflin Kdump: loaded Not tainted 6.6.0
  pc : copy_page+0x10/0xc0
  lr : copy_highpage+0x38/0x50
  ...
  Call trace:
   copy_page+0x10/0xc0
   folio_copy+0x78/0x90
   migrate_folio_extra+0x54/0xa0
   move_to_new_folio+0xd8/0x1f0
   migrate_folio_move+0xb8/0x300
   migrate_pages_batch+0x528/0x788
   migrate_pages_sync+0x8c/0x258
   migrate_pages+0x440/0x528
   soft_offline_in_use_page+0x2ec/0x3c0
   soft_offline_page+0x238/0x310
   soft_offline_page_store+0x6c/0xc0
   dev_attr_store+0x20/0x40
   sysfs_kf_write+0x4c/0x68
   kernfs_fop_write_iter+0x130/0x1c8
   new_sync_write+0xa4/0x138
   vfs_write+0x238/0x2d8
   ksys_write+0x74/0x110

v3:
- only folio migrate recover support part since the cleanup part
  has been merged to mm-unstable
- don't introduce new folio_refs_check_and_freeze(), just move
  the check and freeze folio out, also update changelog 'mm:
  migrate: split folio_migrate_mapping()'
- reorder patches and rebased on next-20240528

v2:
- remove patch11 since fio don't support large folio
- add RB
- rebased on next-20240424

v1:
- no change, resend and rebased on 6.9-rc1

rfcv2:
- Separate __migrate_device_pages() cleanup from patch "remove 
  migrate_folio_extra()", suggested by Matthew
- Split folio_migrate_mapping(), move refcount check/freeze out
  of folio_migrate_mapping(), suggested by Matthew
- add RB

Kefeng Wang (5):
  mm: add folio_mc_copy()
  mm: migrate: split folio_migrate_mapping()
  mm: migrate: support poisoned recover from migrate folio
  fs: hugetlbfs: support poison recover from hugetlbfs_migrate_folio()
  mm: migrate: remove folio_migrate_copy()

 fs/aio.c                |   3 +-
 fs/hugetlbfs/inode.c    |   2 +-
 include/linux/migrate.h |   1 -
 include/linux/mm.h      |   1 +
 mm/migrate.c            | 105 ++++++++++++++++++++++------------------
 mm/util.c               |  20 ++++++++
 6 files changed, 81 insertions(+), 51 deletions(-)