Commit 0c13ed77 authored Mar 29, 2026 by SeongJae Park Committed by Andrew Morton Apr 18, 2026

Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race

DAMON_LRU_SORT handles commit_inputs request inside kdamond thread,
reading the module parameters.  If the user updates the module
parameters while the kdamond thread is reading those, races can happen.
To avoid this, the commit_inputs parameter shows whether it is still in
the progress, assuming users wouldn't update parameters in the middle of
the work.  Some users might ignore that.  Add a warning about the
behavior.

The issue was discovered in [1] by sashiko.

Link: https://lore.kernel.org/20260329153052.46657-3-sj@kernel.org
Link: https://lore.kernel.org/20260319161620.189392-2-objecting@objecting.org

 [1]
Fixes: 6acfcd0d ("Docs/admin-guide/damon: add a document for DAMON_LRU_SORT")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 6.0.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 0beba407

Documentation/admin-guide/mm/damon/lru_sort.rst

+4 −0

Original line number	Diff line number	Diff line
		@@ -79,6 +79,10 @@ of parametrs except ``enabled`` again. Once the re-reading is done, this
		parameter is set as ``N``. If invalid parameters are found while the
		re-reading, DAMON_LRU_SORT will be disabled.

		Once ``Y`` is written to this parameter, the user must not write to any
		parameters until reading ``commit_inputs`` again returns ``N``. If users
		violate this rule, the kernel may exhibit undefined behavior.

		active_mem_bp
		-------------