mm-damon-core-implement-damon_kdamond_pid.patch removed from -mm tree

The quilt patch titled
Subject: mm/damon/core: implement damon_kdamond_pid()
has been removed from the -mm tree. Its filename was
mm-damon-core-implement-damon_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 <[email protected]>
Subject: mm/damon/core: implement damon_kdamond_pid()
Date: Thu, 15 Jan 2026 07:20:41 -0800

Patch series "mm/damon: hide kdamond and kdamond_lock from API callers".

'kdamond' and 'kdamond_lock' fields initially exposed to DAMON API callers for flexible synchronization and use cases. As DAMON API became somewhat complicated compared to the early days, Keeping those exposed could only encourage the API callers to invent more creative but complicated and difficult-to-debug use cases.

Fortunately DAMON API callers didn't invent that many creative use cases. There exist only two use cases of 'kdamond' and 'kdamond_lock'. Finding whether the kdamond is actively running, and getting the pid of the kdamond. For the first use case, a dedicated API function, namely 'damon_is_running()' is provided, and all DAMON API callers are using the function for the use case. Hence only the second use case is where the fields are directly being used by DAMON API callers.

To prevent future invention of complicated and erroneous use cases of the fields, hide the fields from the API callers. For that, provide new dedicated DAMON API functions for the remaining use case, namely damon_kdamond_pid(), migrate DAMON API callers to use the new function, and mark the fields as private fields.

This patch (of 5):

'kdamond' and 'kdamond_lock' are directly being used by DAMON API callers for getting the pid of the corresponding kdamond. To discourage invention of creative but complicated and erroneous new usages of the fields that require careful synchronization, implement a new API function that can simply be used without the manual synchronizations.

---

 include/linux/damon.h |    1 +
 mm/damon/core.c       |   17 +++++++++++++++++
 2 files changed, 18 insertions(+)

@@ -972,6 +972,7 @@ bool damon_initialized(void);
 int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive);
 int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
 bool damon_is_running(struct damon_ctx *ctx);
+int damon_kdamond_pid(struct damon_ctx *ctx);
 
 int damon_call(struct damon_ctx *ctx, struct damon_call_control *control);
 int damos_walk(struct damon_ctx *ctx, struct damos_walk_control *control);

@@ -1442,6 +1442,23 @@ bool damon_is_running(struct damon_ctx *
 	return running;
 }
 
+/**
+ * damon_kdamond_pid() - Return pid of a given DAMON context's worker thread.
+ * @ctx:	The DAMON context of the question.
+ *
+ * Return: pid if @ctx is running, negative error code otherwise.
+ */
+int damon_kdamond_pid(struct damon_ctx *ctx)
+{
+	int pid = -EINVAL;
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond)
+		pid = ctx->kdamond->pid;
+	mutex_unlock(&ctx->kdamond_lock);
+	return pid;
+}
+
 /*
  * damon_call_handle_inactive_ctx() - handle DAMON call request that added to
  *				      an inactive context.

_

Patches currently in -mm which might be from [email protected] are

selftests-damon-sysfs_memcg_path_leaksh-use-kmemleak.patch selftests-damon-wss_estimation-test-for-up-to-160-mib-working-set-size.patch selftests-damon-access_memory-add-repeat-mode.patch selftests-damon-wss_estimation-ensure-number-of-collected-wss.patch selftests-damon-wss_estimation-deduplicate-failed-samples-output.patch mm-damon-remove-damon_operations-cleanup.patch mm-damon-core-cleanup-targets-and-regions-at-once-on-kdamond-termination.patch mm-damon-core-cancel-damos_walk-before-damon_ctx-kdamond-reset.patch mm-damon-core-process-damon_call_control-requests-on-a-local-list.patch mm-damon-document-damon_call_control-dealloc_on_cancel-repeat-behavior.patch mm-damon-core-rename-damos_filter_out-to-damos_core_filter_out.patch mm-damon-rename-damon_min_region-to-damon_min_region_sz.patch mm-damon-rename-min_sz_region-of-damon_ctx-to-min_region_sz.patch docs-mm-damon-index-simplify-the-intro.patch docs-mm-damon-design-link-repology-instead-of-fedora-package.patch docs-mm-damon-design-document-damon-sample-modules.patch docs-mm-damon-design-add-reference-to-damon_stat-usage.patch docs-admin-guide-mm-damon-usage-introduce-damon-modules-at-the-beginning.patch docs-admin-guide-mm-damon-usage-update-stats-update-process-for-refresh_ms.patch docs-mm-damon-maintainer-profile-fix-wrong-maitnainers-section-name.patch docs-mm-damon-maintainer-profile-remove-damon-tests-perf-suggestion.patch maple_tree-start-using-maple-copy-node-for-destination-fix.patch