linux-kernel - [RFC PATCH 11/12] mm/cma: rebalance CMA when changing cma_first

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Message-ID: <20250915195153.462039-12-fvdl@google.com>
Date: Mon, 15 Sep 2025 19:51:52 +0000
From: Frank van der Linden <fvdl@...gle.com>
To: akpm@...ux-foundation.org, muchun.song@...ux.dev, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Cc: hannes@...xchg.org, david@...hat.com, roman.gushchin@...ux.dev, 
	Frank van der Linden <fvdl@...gle.com>
Subject: [RFC PATCH 11/12] mm/cma: rebalance CMA when changing cma_first_limit

To keep things consistent, rebalance CMA when changing the
cma_first_limit sysctl.

Signed-off-by: Frank van der Linden <fvdl@...gle.com>
---
 mm/page_alloc.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index dc59aaa63ae6..da1cab63995c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6640,6 +6640,24 @@ static int percpu_pagelist_high_fraction_sysctl_handler(const struct ctl_table *
 	return ret;
 }
 
+#ifdef CONFIG_CMA
+static int cma_first_limit_sysctl_handler(const struct ctl_table *table,
+				int write, void *buffer, size_t *length,
+				loff_t *ppos)
+{
+	int ret, nid;
+
+	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (ret || !write)
+		return ret;
+
+	for_each_node_state(nid, N_MEMORY)
+		balance_node_cma(nid, NULL);
+
+	return 0;
+}
+#endif
+
 static const struct ctl_table page_alloc_sysctl_table[] = {
 	{
 		.procname	= "min_free_kbytes",
@@ -6723,7 +6741,7 @@ static const struct ctl_table page_alloc_sysctl_table[] = {
 		.data		= &cma_first_limit,
 		.maxlen		= sizeof(cma_first_limit),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
+		.proc_handler	= cma_first_limit_sysctl_handler,
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE_HUNDRED,
 	},
-- 
2.51.0.384.g4c02a37b29-goog