+ docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch added to mm-hotfixes-unstable branch

+ docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race
Date: Sun, 29 Mar 2026 08:30:50 -0700

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://lkml.kernel.org/r/20260329153052.46657-3-sj@kernel.org
Link: https://lore.kernel.org/20260319161620.189392-2-objecting@objecting.org [1]
Fixes: 6acfcd0d7524 ("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>
---

 Documentation/admin-guide/mm/damon/lru_sort.rst |    4 ++++
 1 file changed, 4 insertions(+)

--- a/Documentation/admin-guide/mm/damon/lru_sort.rst~docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race
+++ a/Documentation/admin-guide/mm/damon/lru_sort.rst
@@ -79,6 +79,10 @@ of parametrs except ``enabled`` again.
 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
 -------------
 
_

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-sysfs-dealloc-repeat_call_control-if-damon_call-fails.patch
mm-damon-core-fix-damon_call-vs-kdamond_fn-exit-race.patch
mm-damon-core-fix-damos_walk-vs-kdamond_fn-exit-race.patch
mm-damon-core-validate-damos_quota_goal-nid-for-node_mem_usedfree_bp.patch
mm-damon-core-validate-damos_quota_goal-nid-for-node_memcg_usedfree_bp.patch
mm-damon-core-use-time_in_range_open-for-damos-quota-window-start.patch
docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch
docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch