linux-kernel - [RFC PATCH v1 2/3] mm/damon/core: Add damon_start

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Date:   Fri, 18 Feb 2022 19:26:10 +0900
From:   Jonghyeon Kim <tome01@...u.ac.kr>
To:     akpm@...ux-foundation.org
Cc:     Jonghyeon Kim <tome01@...u.ac.kr>, Jonathan.Cameron@...wei.com,
        amit@...nel.org, benh@...nel.crashing.org, corbet@....net,
        david@...hat.com, dwmw@...zon.com, elver@...gle.com,
        foersleo@...zon.de, gthelen@...gle.com, markubo@...zon.de,
        rientjes@...gle.com, shakeelb@...gle.com, shuah@...nel.org,
        linux-damon@...zon.com, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 2/3] mm/damon/core: Add damon_start_one()

damon_start() function is designed to start multiple damon monitoring
contexts. But, sometimes we need to start monitoring one context.
Although __damon_start() could be considered to start for one monitoring
context, it seems reasonable to adopt a new function that does not need
to handle 'damon_lock' from the caller.

Signed-off-by: Jonghyeon Kim <tome01@...u.ac.kr>
---
 include/linux/damon.h |  1 +
 mm/damon/core.c       | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index c0adf1566603..069577477662 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -511,6 +511,7 @@ int damon_register_ops(struct damon_operations *ops);
 int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id);
 
 int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
+int damon_start_one(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
 
 #endif	/* CONFIG_DAMON */
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 290c9c0535ee..e43f138a3489 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -466,6 +466,31 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs)
 	return err;
 }
 
+/**
+ * damon_start_one() - Starts the monitorings for one context.
+ * @ctx:	monitoring context
+ *
+ * This function starts one monitoring thread for only one monitoring context
+ * handling damon_lock.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_start_one(struct damon_ctx *ctx)
+{
+	int err = 0;
+
+	mutex_lock(&damon_lock);
+	err = __damon_start(ctx);
+	if (err) {
+		mutex_unlock(&damon_lock);
+		return err;
+	}
+	nr_running_ctxs++;
+	mutex_unlock(&damon_lock);
+
+	return err;
+}
+
 /*
  * __damon_stop() - Stops monitoring of given context.
  * @ctx:	monitoring context
-- 
2.17.1