[RFC PATCH 09/18] mm/damon/sysfs: move sysfs_lock to common module

[SeongJae Park <sj@kernel.org>]

DAMON sysfs interface is implemented in a single file, sysfs.c, which
has about 2,800 lines of code.  As the interface is hierarchical and
some of the code can be reused by different hierarchies, it would make
more sense to split the implementation into common parts and different
parts in multiple files.  As the beginning of the work, create files for
common code and move the global mutex for directories modifications
protection into the files.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/Makefile       |  2 +-
 mm/damon/sysfs-common.c | 11 +++++++++++
 mm/damon/sysfs-common.h | 11 +++++++++++
 mm/damon/sysfs.c        |  4 +---
 4 files changed, 24 insertions(+), 4 deletions(-)
 create mode 100644 mm/damon/sysfs-common.c
 create mode 100644 mm/damon/sysfs-common.h

diff --git a/mm/damon/Makefile b/mm/damon/Makefile
index a076ccd55d44..50d6b2ab3956 100644
--- a/mm/damon/Makefile
+++ b/mm/damon/Makefile
@@ -3,7 +3,7 @@
 obj-y				:= core.o
 obj-$(CONFIG_DAMON_VADDR)	+= ops-common.o vaddr.o
 obj-$(CONFIG_DAMON_PADDR)	+= ops-common.o paddr.o
-obj-$(CONFIG_DAMON_SYSFS)	+= sysfs.o
+obj-$(CONFIG_DAMON_SYSFS)	+= sysfs-common.o sysfs.o
 obj-$(CONFIG_DAMON_DBGFS)	+= dbgfs.o
 obj-$(CONFIG_DAMON_RECLAIM)	+= modules-common.o reclaim.o
 obj-$(CONFIG_DAMON_LRU_SORT)	+= modules-common.o lru_sort.o
diff --git a/mm/damon/sysfs-common.c b/mm/damon/sysfs-common.c
new file mode 100644
index 000000000000..9dc743868d5b
--- /dev/null
+++ b/mm/damon/sysfs-common.c
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Common Primitives for DAMON Sysfs Interface
+ *
+ * Author: SeongJae Park <sj@kernel.org>
+ */
+
+#include "sysfs-common.h"
+
+DEFINE_MUTEX(damon_sysfs_lock);
+
diff --git a/mm/damon/sysfs-common.h b/mm/damon/sysfs-common.h
new file mode 100644
index 000000000000..745a918b94f5
--- /dev/null
+++ b/mm/damon/sysfs-common.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common Primitives for DAMON Sysfs Interface
+ *
+ * Author: SeongJae Park <sj@kernel.org>
+ */
+
+#include <linux/damon.h>
+#include <linux/kobject.h>
+
+extern struct mutex damon_sysfs_lock;
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index e8bd7367d15b..0f3f06d8dae7 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -5,13 +5,11 @@
  * Copyright (c) 2022 SeongJae Park <sj@kernel.org>
  */
 
-#include <linux/damon.h>
-#include <linux/kobject.h>
 #include <linux/pid.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 
-static DEFINE_MUTEX(damon_sysfs_lock);
+#include "sysfs-common.h"
 
 /*
  * unsigned long range directory
-- 
2.25.1