linux-kernel - [PATCH 5/5] mm/damon/sysfs: decouple from damon_ops

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Message-Id: <20250622213759.50930-6-sj@kernel.org>
Date: Sun, 22 Jun 2025 14:37:59 -0700
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
	damon@...ts.linux.dev,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 5/5] mm/damon/sysfs: decouple from damon_ops_id

Decouple DAMON sysfs interface from damon_ops_id.  For this, define and
use new mm/damon/sysfs.c internal data structure that maps the
user-space keywords and damon_ops_id, instead of having the implicit and
unflexible array index rule.

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/damon/sysfs.c | 56 +++++++++++++++++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 15 deletions(-)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 1af6aff35d84..1b1476b79cdb 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -811,11 +811,24 @@ static const struct kobj_type damon_sysfs_attrs_ktype = {
  * context directory
  */
 
-/* This should match with enum damon_ops_id */
-static const char * const damon_sysfs_ops_strs[] = {
-	"vaddr",
-	"fvaddr",
-	"paddr",
+struct damon_sysfs_ops_name {
+	enum damon_ops_id ops_id;
+	char *name;
+};
+
+static const struct damon_sysfs_ops_name damon_sysfs_ops_names[] = {
+	{
+		.ops_id = DAMON_OPS_VADDR,
+		.name = "vaddr",
+	},
+	{
+		.ops_id = DAMON_OPS_FVADDR,
+		.name = "fvaddr",
+	},
+	{
+		.ops_id = DAMON_OPS_PADDR,
+		.name = "paddr",
+	},
 };
 
 struct damon_sysfs_context {
@@ -934,14 +947,16 @@ static void damon_sysfs_context_rm_dirs(struct damon_sysfs_context *context)
 static ssize_t avail_operations_show(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
-	enum damon_ops_id id;
 	int len = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(damon_sysfs_ops_names); i++) {
+		const struct damon_sysfs_ops_name *ops_name;
 
-	for (id = 0; id < NR_DAMON_OPS; id++) {
-		if (!damon_is_registered_ops(id))
+		ops_name = &damon_sysfs_ops_names[i];
+		if (!damon_is_registered_ops(ops_name->ops_id))
 			continue;
-		len += sysfs_emit_at(buf, len, "%s\n",
-				damon_sysfs_ops_strs[id]);
+		len += sysfs_emit_at(buf, len, "%s\n", ops_name->name);
 	}
 	return len;
 }
@@ -951,8 +966,16 @@ static ssize_t operations_show(struct kobject *kobj,
 {
 	struct damon_sysfs_context *context = container_of(kobj,
 			struct damon_sysfs_context, kobj);
+	int i;
 
-	return sysfs_emit(buf, "%s\n", damon_sysfs_ops_strs[context->ops_id]);
+	for (i = 0; i < ARRAY_SIZE(damon_sysfs_ops_names); i++) {
+		const struct damon_sysfs_ops_name *ops_name;
+
+		ops_name = &damon_sysfs_ops_names[i];
+		if (ops_name->ops_id == context->ops_id)
+			return sysfs_emit(buf, "%s\n", ops_name->name);
+	}
+	return -EINVAL;
 }
 
 static ssize_t operations_store(struct kobject *kobj,
@@ -960,11 +983,14 @@ static ssize_t operations_store(struct kobject *kobj,
 {
 	struct damon_sysfs_context *context = container_of(kobj,
 			struct damon_sysfs_context, kobj);
-	enum damon_ops_id id;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(damon_sysfs_ops_names); i++) {
+		const struct damon_sysfs_ops_name *ops_name;
 
-	for (id = 0; id < NR_DAMON_OPS; id++) {
-		if (sysfs_streq(buf, damon_sysfs_ops_strs[id])) {
-			context->ops_id = id;
+		ops_name = &damon_sysfs_ops_names[i];
+		if (sysfs_streq(buf, ops_name->name)) {
+			context->ops_id = ops_name->ops_id;
 			return count;
 		}
 	}
-- 
2.39.5