Callers of damon_call() should validate the damon_ctx object parameter.
If it is NULL or never damon_start()-ed object, damon_call() could
dereference the NULL pointer or indefinitely hang.  Ensuring all callers
doing the validation correctly has turned out to be difficult.  Handle
the corner cases inside the core layer and remove callers' validations.

Patches 1 and 2 respectively allow passing NULL and not yet
damon_start()-ed ctx parameter to damon_call().  Patches 3 and 4 remove
the callers side validations in DMON_RECLAIM and DASMON_LRU_SORT,
respectively.

Changes from RFC
- RFC: https://lore.kernel.org/20260813035001.97364-1-sj@kernel.org
- Drop RFC tag.
- Rebase to lates mm-new.

SJ Park (4):
  mm/damon/core: handle NULL ctx parameter in damon_call()
  mm/damon/core: set ctx->call_controls_obsolete in damon_new_ctx()
  mm/damon/reclaim: remove unnecessary damon_call() param validation
  mm/damon/lru_sort: remove unnecessary damon_call() param validation

 mm/damon/core.c     | 7 +++----
 mm/damon/lru_sort.c | 8 --------
 mm/damon/reclaim.c  | 8 --------
 3 files changed, 3 insertions(+), 20 deletions(-)


base-commit: 7fe9a8a366a72a631bcb23c2b108669ab182f2f2
-- 
2.47.3

On Wed,  2 Sep 2026 18:03:29 -0700 SJ Park <sj@kernel.org> wrote:

> Callers of damon_call() should validate the damon_ctx object parameter.
> If it is NULL or never damon_start()-ed object, damon_call() could
> dereference the NULL pointer or indefinitely hang.  Ensuring all callers
> doing the validation correctly has turned out to be difficult.  Handle
> the corner cases inside the core layer and remove callers' validations.

Sashiko found no blocker for this series.  Sashiko sent its findings to damon@
mailing list [1], and I replied to all the comments having findings other than
the absence of issues.  Please read those for details.

[1] https://lore.kernel.org/damon/


Thanks,
SJ

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