[PATCH rfc 0/9] mm: migrate: support poison recover from migrate folio

[Kefeng Wang <wangkefeng.wang@huawei.com>]

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 kerenl will
panic.

There is a mechanism in the kernel to recover from uncorrectable memory
errors, ARCH_HAS_COPY_MC(Machine Check Safe Memory Copy), 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

Kefeng Wang (9):
  mm: migrate: simplify __buffer_migrate_folio()
  mm: migrate_device: use more folio in __migrate_device_pages()
  mm: migrate: remove migrate_folio_extra()
  mm: remove MIGRATE_SYNC_NO_COPY mode
  mm: add folio_mc_copy()
  mm: migrate: support poisoned folio copy recover from migrate folio
  fs: hugetlbfs: support poison recover from hugetlbfs_migrate_folio()
  mm: migrate: remove folio_migrate_copy()
  fs: aio: add explicit check for large folio in aio_migrate_folio()

 fs/aio.c                     | 15 +++------
 fs/hugetlbfs/inode.c         | 13 +++++---
 include/linux/migrate.h      |  4 +--
 include/linux/migrate_mode.h |  5 ---
 include/linux/mm.h           |  1 +
 mm/balloon_compaction.c      |  8 -----
 mm/migrate.c                 | 64 +++++++++++-------------------------
 mm/migrate_device.c          | 26 +++++++--------
 mm/util.c                    | 20 +++++++++++
 mm/zsmalloc.c                |  8 -----
 10 files changed, 69 insertions(+), 95 deletions(-)

-- 
2.27.0