[RFC PATCH v4 0/7] snapshot_set_swap_area() unpins the previously selected swap device and

[SJ Park <sj@kernel.org>]

Add repin_hibernation_swap_type(), which looks up the new device, clears
the old SWP_HIBERNATION flag and sets the new one under a single swap_lock
acquisition.  The same-device case is short- circuited so userspace can
re-select the same swap area without tripping WARN_ON_ONCE and -EBUSY. 
Switch snapshot_set_swap_area() to the new helper.

A failed lookup now preserves the previous pin instead of dropping it, so
a bad SNAPSHOT_SET_SWAP_AREA leaves the prior selection intact.  The open
and release paths keep using pin_hibernation_swap_type() and
unpin_hibernation_swap_type().

The race was identified during AI-assisted review of the SWP_HIBERNATION
pinning series.

SJ Park (7):
  mm/damon/core: introduce damos_quota_goal->complement
  mm/damon/core: add complement argument to damos_new_quota_goal()
  mm/damon/sysfs-schemes: support quota goal complement flag
  mm/damon/tests/core-kunit: test quota_goal->complement commit
  Docs/mm/damon/design: document damos quota goal complement flag
  Docs/admin-guide/mm/damon/usage: update for quota goal complement file
  Docs/ABI/damon: update for quota goal metric complement sysfs file

 .../ABI/testing/sysfs-kernel-mm-damon         |  6 ++++
 Documentation/admin-guide/mm/damon/usage.rst  | 15 +++++----
 Documentation/mm/damon/design.rst             | 15 ++++++---
 include/linux/damon.h                         |  4 ++-
 mm/damon/core.c                               | 33 ++++++++++++++++---
 mm/damon/lru_sort.c                           |  5 +--
 mm/damon/reclaim.c                            |  5 +--
 mm/damon/sysfs-schemes.c                      | 30 +++++++++++++++++
 mm/damon/tests/core-kunit.h                   |  3 ++
 samples/damon/mtier.c                         |  2 +-
 10 files changed, 97 insertions(+), 21 deletions(-)


base-commit: 1c2b8d2725f84b43fabe3b3e9628c91db8ca6c65
-- 
2.47.3