[merged mm-stable] mm-damon-stat-add-a-parameter-for-reading-kdamond-pid.patch removed from -mm tree

[merged mm-stable] mm-damon-stat-add-a-parameter-for-reading-kdamond-pid.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/damon/stat: add a parameter for reading kdamond pid
has been removed from the -mm tree.  Its filename was
     mm-damon-stat-add-a-parameter-for-reading-kdamond-pid.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/stat: add a parameter for reading kdamond pid
Date: Fri, 1 May 2026 19:05:03 -0700

Patch series "mm/damon/stat: add kdamond_pid parameter".

DAMON_STAT doesn't provide the pid of its kdamond, unlike DAMON_RECLAIM
and DAMON_LRU_SORT.  This makes user-space management of DAMON_STAT
unnecessarily complicated.  Provide the information via a new parameter,
namely kdamond_pid, and document it.


This patch (of 2):

Knowing the pid of the kdamonds can help user-space management including
monitoring of DAMON's system resource consumption.  To make it easier,
DAMON_SYSFS, DAMON_RECLAIM and DAMON_LRU_SORT provide the pid information.
DAMON_STAT is not providing it, though.  Expose the pid of DAMON_STAT
kdamond via a new read-only module parameter, namely kdamond_pid.  This
also makes DAMON modules usage more standardized, because DAMON_RECLAIM
and DAMON_LRU_SORT also provide the information via their read-only
parameters of the same name.

Link: https://lore.kernel.org/20260502020505.80822-1-sj@kernel.org
Link: https://lore.kernel.org/20260502020505.80822-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/stat.c |   39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

--- a/mm/damon/stat.c~mm-damon-stat-add-a-parameter-for-reading-kdamond-pid
+++ a/mm/damon/stat.c
@@ -266,6 +266,45 @@ static int damon_stat_enabled_load(char
 	return sprintf(buffer, "%c\n", damon_stat_enabled() ? 'Y' : 'N');
 }
 
+static int damon_stat_kdamond_pid_store(
+		const char *val, const struct kernel_param *kp)
+{
+	/*
+	 * kdamond_pid is read-only, but kernel command line could write it.
+	 * Do nothing here.
+	 */
+	return 0;
+}
+
+static int damon_stat_kdamond_pid_load(
+		char *buffer, const struct kernel_param *kp)
+{
+	int pid;
+
+	if (!damon_stat_context) {
+		pid = -1;
+	} else {
+		pid = damon_kdamond_pid(damon_stat_context);
+		if (pid < 1)
+			pid = -1;
+	}
+	return sprintf(buffer, "%d\n", pid);
+}
+
+static const struct kernel_param_ops kdamond_pid_param_ops = {
+	.set = damon_stat_kdamond_pid_store,
+	.get = damon_stat_kdamond_pid_load,
+};
+
+/*
+ * PID of the DAMON thread
+ *
+ * If DAMON_STAT is enabled, this becomes the PID of the worker thread.
+ * Else, -1.
+ */
+module_param_cb(kdamond_pid, &kdamond_pid_param_ops, NULL, 0400);
+MODULE_PARM_DESC(kdamond_pid, "pid of the kdamond");
+
 static int __init damon_stat_init(void)
 {
 	int err = 0;
_

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

mm-damon-ops-common-call-folio_test_lru-after-folio_get.patch
mm-damon-reclaim-handle-ctx-allocation-failure.patch
mm-damonn-lru_sort-handle-ctx-allocation-failure.patch
mm-damon-core-introduce-struct-damon_probe.patch
mm-damon-core-embed-damon_probe-objects-in-damon_ctx.patch
mm-damon-core-introduce-damon_filter.patch
mm-damon-core-commit-probes.patch
mm-damon-core-introduce-damon_region-probe_hits.patch
mm-damon-core-introduce-damon_ops-apply_probes.patch
mm-damon-core-do-data-attributes-monitoring.patch
mm-damon-paddr-support-data-attributes-monitoring.patch
mm-damon-sysfs-implement-probes-dir.patch
mm-damon-sysfs-implement-probe-dir.patch
mm-damon-sysfs-implement-filters-directory.patch
mm-damon-sysfs-implement-filter-dir.patch
mm-damon-sysfs-implement-filter-dir-files.patch
mm-damon-sysfs-setup-probes-on-damon-core-api-parameters.patch
mm-damon-sysfs-schemes-implement-tried_regions-r-probes.patch
mm-damon-sysfs-schemes-implement-probe-dir.patch
mm-damon-sysfs-schemes-implement-probe-hits-file.patch
mm-damon-trace-probe_hits.patch
selftests-damon-sysfssh-test-probes-dir.patch
docs-mm-damon-design-document-data-attributes-monitoring.patch
docs-admin-guide-mm-damon-usage-document-data-attributes-monitoring.patch
mm-damon-core-introduce-damon_filter_type_memcg.patch
mm-damon-paddr-support-damon_filter_type_memcg.patch
mm-damon-sysfs-add-filters-f-path-file.patch
mm-damon-sysfs-schemes-move-memcg_path_to_id-to-sysfs-common.patch
mm-damon-sysfs-setup-damon_filter-memcg_id-from-path.patch
docs-mm-damon-design-update-for-memcg-damon-filter.patch
docs-admin-guide-mm-damon-usage-update-for-memcg-damon-filter.patch
mm-damon-core-safely-handle-no-region-case-in-damon_set_regions.patch
mm-damon-core-do-not-use-region-out-of-a-loop-in-damon_set_regions.patch
samples-damon-mtier-replace-damon_add_region-with-damon_set_regions.patch
mm-damon-tests-vaddr-kunit-replace-damon_add_region-with-damon_set_regions.patch
mm-damon-core-hide-damon_add_region.patch
mm-damon-core-hide-damon_insert_region.patch
mm-damon-core-hide-damon_destroy_region.patch
mm-damon-core-add-kdamond_call-debug_sanity-check.patch
mm-damon-core-remove-damon_verify_nr_regions.patch
mm-damon-tests-core-kunit-add-damon_set_regions-test-cases.patch
selftests-damon-sysfspy-stop-kdamonds-before-failing.patch
selftests-damon-sysfssh-test-monitoring-intervals-goal-dir.patch
selftests-damon-sysfssh-test-addr_unit-file-existence.patch
selftests-damon-sysfssh-test-pause-file-existence.patch
mm-damon-core-trace-esz-at-first-setup.patch