From 0ec282155c8458954b886a8d0045a753d6c5a207 Mon Sep 17 00:00:00 2001
From: Jakov Novak <jakovnovak30@gmail.com>
Date: Thu, 30 Jul 2026 22:47:24 +0200
Subject: [PATCH] mm/khugepaged: replace mutex_lock/mutex_unlock usage with
 guard macro

Currently, khugepaged locks the khugepaged_mutex in two functions:
start_stop_khugepaged and khugepaged_min_free_kbytes_update.  Remove
mutex_lock/mutex_unlock usage in these functions and replace it with the
guard macro.  This makes the code more readable (removing a goto
statement) and makes it harder to introduce bugs in the future.  No
functional changes introduced.

Link: https://lore.kernel.org/20260730204724.16912-1-jakovnovak30@gmail.com
Signed-off-by: Jakov Novak <jakovnovak30@gmail.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/khugepaged.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 27e8f3077e80..b237f6e7662a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -23,6 +23,7 @@
 #include <linux/ksm.h>
 #include <linux/pgalloc.h>
 #include <linux/backing-dev.h>
+#include <linux/cleanup.h>
 
 #include <asm/tlb.h>
 #include "internal.h"
@@ -3115,18 +3116,19 @@ void set_recommended_min_free_kbytes(void)
 
 int start_stop_khugepaged(void)
 {
-	int err = 0;
-
-	mutex_lock(&khugepaged_mutex);
+	guard(mutex)(&khugepaged_mutex);
 	if (hugepage_enabled()) {
-		if (!khugepaged_thread)
-			khugepaged_thread = kthread_run(khugepaged, NULL,
-							"khugepaged");
-		if (IS_ERR(khugepaged_thread)) {
-			pr_err("khugepaged: kthread_run(khugepaged) failed\n");
-			err = PTR_ERR(khugepaged_thread);
-			khugepaged_thread = NULL;
-			goto fail;
+		if (!khugepaged_thread) {
+			struct task_struct *new_thread = kthread_run(khugepaged,
+								     NULL,
+								     "khugepaged");
+
+			if (IS_ERR(new_thread)) {
+				pr_err("khugepaged: kthread_run(khugepaged) failed\n");
+				return PTR_ERR(new_thread);
+			}
+
+			khugepaged_thread = new_thread;
 		}
 
 		if (!list_empty(&khugepaged_scan.mm_head))
@@ -3136,17 +3138,14 @@ int start_stop_khugepaged(void)
 		khugepaged_thread = NULL;
 	}
 	set_recommended_min_free_kbytes();
-fail:
-	mutex_unlock(&khugepaged_mutex);
-	return err;
+	return 0;
 }
 
 void khugepaged_min_free_kbytes_update(void)
 {
-	mutex_lock(&khugepaged_mutex);
+	guard(mutex)(&khugepaged_mutex);
 	if (hugepage_enabled() && khugepaged_thread)
 		set_recommended_min_free_kbytes();
-	mutex_unlock(&khugepaged_mutex);
 }
 
 bool current_is_khugepaged(void)