[RFC PATCH 1/3] mm/lru_gen: refactor to extract helper functions

[Jiayuan Chen <jiayuan.chen@linux.dev>]

From: Jiayuan Chen <jiayuan.chen@shopee.com>

Extract helper functions from debugfs interface for code reuse:

- lru_gen_print_lruvec(): Print generations for a single lruvec,
  extracted from lru_gen_seq_show().

- __run_cmd(): Core command execution logic, extracted from run_cmd().

These helpers will be used by the upcoming memcg interface.
No functional change.

Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
---
 mm/vmscan.c | 82 +++++++++++++++++++++++++++++++----------------------
 1 file changed, 48 insertions(+), 34 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 619691aa4393..8ea5b67daa36 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5397,29 +5397,13 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
 	seq_putc(m, '\n');
 }
 
-/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
-static int lru_gen_seq_show(struct seq_file *m, void *v)
+/* Print generations for a single lruvec - helper for debugfs and memcg */
+static void lru_gen_print_lruvec(struct seq_file *m, struct lruvec *lruvec,
+				 unsigned long max_seq, unsigned long *min_seq,
+				 bool full)
 {
 	unsigned long seq;
-	bool full = debugfs_get_aux_num(m->file);
-	struct lruvec *lruvec = v;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
-	int nid = lruvec_pgdat(lruvec)->node_id;
-	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
-	DEFINE_MAX_SEQ(lruvec);
-	DEFINE_MIN_SEQ(lruvec);
-
-	if (nid == first_memory_node) {
-		const char *path = memcg ? m->private : "";
-
-#ifdef CONFIG_MEMCG
-		if (memcg)
-			cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
-#endif
-		seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
-	}
-
-	seq_printf(m, " node %5d\n", nid);
 
 	if (!full)
 		seq = evictable_min_seq(min_seq, MAX_SWAPPINESS / 2);
@@ -5431,7 +5415,7 @@ static int lru_gen_seq_show(struct seq_file *m, void *v)
 	for (; seq <= max_seq; seq++) {
 		int type, zone;
 		int gen = lru_gen_from_seq(seq);
-		unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
+		unsigned long birth = READ_ONCE(lrugen->timestamps[gen]);
 
 		seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth));
 
@@ -5450,7 +5434,31 @@ static int lru_gen_seq_show(struct seq_file *m, void *v)
 		if (full)
 			lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq);
 	}
+}
+
+/* see Documentation/admin-guide/mm/multigen_lru.rst for details */
+static int lru_gen_seq_show(struct seq_file *m, void *v)
+{
+	bool full = debugfs_get_aux_num(m->file);
+	struct lruvec *lruvec = v;
+	int nid = lruvec_pgdat(lruvec)->node_id;
+	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+	DEFINE_MAX_SEQ(lruvec);
+	DEFINE_MIN_SEQ(lruvec);
+
+	if (nid == first_memory_node) {
+		const char *path = memcg ? m->private : "";
+
+#ifdef CONFIG_MEMCG
+		if (memcg)
+			cgroup_path(memcg->css.cgroup, m->private, PATH_MAX);
+#endif
+		seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path);
+	}
 
+	seq_printf(m, " node %5d\n", nid);
+
+	lru_gen_print_lruvec(m, lruvec, max_seq, min_seq, full);
 	return 0;
 }
 
@@ -5501,6 +5509,24 @@ static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_co
 	return -EINTR;
 }
 
+/* Core command execution - helper for debugfs and memcg */
+static int __run_cmd(char cmd, struct lruvec *lruvec, unsigned long seq,
+		     struct scan_control *sc, int swappiness, unsigned long opt)
+{
+	if (swappiness < MIN_SWAPPINESS)
+		swappiness = get_swappiness(lruvec, sc);
+	else if (swappiness > SWAPPINESS_ANON_ONLY)
+		return -EINVAL;
+
+	switch (cmd) {
+	case '+':
+		return run_aging(lruvec, seq, swappiness, opt);
+	case '-':
+		return run_eviction(lruvec, seq, sc, swappiness, opt);
+	}
+	return -EINVAL;
+}
+
 static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
 		   struct scan_control *sc, int swappiness, unsigned long opt)
 {
@@ -5530,19 +5556,7 @@ static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq,
 	sc->target_mem_cgroup = memcg;
 	lruvec = get_lruvec(memcg, nid);
 
-	if (swappiness < MIN_SWAPPINESS)
-		swappiness = get_swappiness(lruvec, sc);
-	else if (swappiness > SWAPPINESS_ANON_ONLY)
-		goto done;
-
-	switch (cmd) {
-	case '+':
-		err = run_aging(lruvec, seq, swappiness, opt);
-		break;
-	case '-':
-		err = run_eviction(lruvec, seq, sc, swappiness, opt);
-		break;
-	}
+	err = __run_cmd(cmd, lruvec, seq, sc, swappiness, opt);
 done:
 	mem_cgroup_put(memcg);
 
-- 
2.43.0