mm/damon/modules: deduplicate init steps for DAMON context setup

DAMON_RECLAIM and DAMON_LRU_SORT has duplicated code for DAMON context and
target initializations.  Deduplicate the part by implementing a function
for the initialization in 'modules-common.c' and using it.

Link: https://lkml.kernel.org/r/20221026225943.100429-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/Makefile

@@ -5,5 +5,5 @@ obj-$(CONFIG_DAMON_VADDR)	+= ops-common.o vaddr.o
 obj-$(CONFIG_DAMON_PADDR)	+= ops-common.o paddr.o
 obj-$(CONFIG_DAMON_SYSFS)	+= sysfs-common.o sysfs-schemes.o sysfs.o
 obj-$(CONFIG_DAMON_DBGFS)	+= dbgfs.o
-obj-$(CONFIG_DAMON_RECLAIM)	+= reclaim.o
+obj-$(CONFIG_DAMON_RECLAIM)	+= modules-common.o reclaim.o
-obj-$(CONFIG_DAMON_LRU_SORT)	+= lru_sort.o
+obj-$(CONFIG_DAMON_LRU_SORT)	+= modules-common.o lru_sort.o

mm/damon/lru_sort.c

@@ -314,25 +314,14 @@ static int damon_lru_sort_after_wmarks_check(struct damon_ctx *c)
 
 static int __init damon_lru_sort_init(void)
 {
-	ctx = damon_new_ctx();
+	int err = damon_modules_new_paddr_ctx_target(&ctx, &target);
-	if (!ctx)
-		return -ENOMEM;
 
-	if (damon_select_ops(ctx, DAMON_OPS_PADDR)) {
+	if (err)
-		damon_destroy_ctx(ctx);
+		return err;
-		return -EINVAL;
-	}
 
 	ctx->callback.after_wmarks_check = damon_lru_sort_after_wmarks_check;
 	ctx->callback.after_aggregation = damon_lru_sort_after_aggregation;
 
-	target = damon_new_target();
-	if (!target) {
-		damon_destroy_ctx(ctx);
-		return -ENOMEM;
-	}
-	damon_add_target(ctx, target);
-
 	schedule_delayed_work(&damon_lru_sort_timer, 0);
 
 	damon_lru_sort_initialized = true;

mm/damon/modules-common.c

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Common Primitives for DAMON Modules
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#include <linux/damon.h>
+
+#include "modules-common.h"
+
+/*
+ * Allocate, set, and return a DAMON context for the physical address space.
+ * @ctxp:	Pointer to save the point to the newly created context
+ * @targetp:	Pointer to save the point to the newly created target
+ */
+int damon_modules_new_paddr_ctx_target(struct damon_ctx **ctxp,
+		struct damon_target **targetp)
+{
+	struct damon_ctx *ctx;
+	struct damon_target *target;
+
+	ctx = damon_new_ctx();
+	if (!ctx)
+		return -ENOMEM;
+
+	if (damon_select_ops(ctx, DAMON_OPS_PADDR)) {
+		damon_destroy_ctx(ctx);
+		return -EINVAL;
+	}
+
+	target = damon_new_target();
+	if (!target) {
+		damon_destroy_ctx(ctx);
+		return -ENOMEM;
+	}
+	damon_add_target(ctx, target);
+
+	*ctxp = ctx;
+	*targetp = target;
+	return 0;
+}

mm/damon/modules-common.h

@@ -44,3 +44,6 @@
 			0400);						\
 	module_param_named(nr_##qt_exceed_name, stat.qt_exceeds, ulong,	\
 			0400);
+
+int damon_modules_new_paddr_ctx_target(struct damon_ctx **ctxp,
+		struct damon_target **targetp);

mm/damon/reclaim.c

@@ -256,25 +256,14 @@ static int damon_reclaim_after_wmarks_check(struct damon_ctx *c)
 
 static int __init damon_reclaim_init(void)
 {
-	ctx = damon_new_ctx();
+	int err = damon_modules_new_paddr_ctx_target(&ctx, &target);
-	if (!ctx)
-		return -ENOMEM;
 
-	if (damon_select_ops(ctx, DAMON_OPS_PADDR)) {
+	if (err)
-		damon_destroy_ctx(ctx);
+		return err;
-		return -EINVAL;
-	}
 
 	ctx->callback.after_wmarks_check = damon_reclaim_after_wmarks_check;
 	ctx->callback.after_aggregation = damon_reclaim_after_aggregation;
 
-	target = damon_new_target();
-	if (!target) {
-		damon_destroy_ctx(ctx);
-		return -ENOMEM;
-	}
-	damon_add_target(ctx, target);
-
 	schedule_delayed_work(&damon_reclaim_timer, 0);
 
 	damon_reclaim_initialized = true;