linux-kernel - [PATCH v3 1/2] drivers/base/memory: Improve add_boot_memory

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Message-ID: <20250311233045.148943-2-gshan@redhat.com>
Date: Wed, 12 Mar 2025 09:30:43 +1000
From: Gavin Shan <gshan@...hat.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	david@...hat.com,
	osalvador@...e.de,
	gregkh@...uxfoundation.org,
	rafael@...nel.org,
	dakr@...nel.org,
	akpm@...ux-foundation.org,
	shan.gavin@...il.com
Subject: [PATCH v3 1/2] drivers/base/memory: Improve add_boot_memory_block()

It's unnecessary to count the present sections for the specified
block since the block will be added if any section in the block
is present. Besides, for_each_present_section_nr() can be reused
as Andrew Morton suggested.

Improve by using for_each_present_section_nr() and dropping the
unnecessary @section_count.

No functional changes intended.

Signed-off-by: Gavin Shan <gshan@...hat.com>
Acked-by: David Hildenbrand <david@...hat.com>
Acked-by: Oscar Salvador <osalvador@...e.de>
---
 drivers/base/memory.c  | 17 ++++++++---------
 include/linux/mmzone.h |  5 +++++
 mm/sparse.c            |  5 -----
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 348c5dbbfa68..f66e9d537c12 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -822,18 +822,17 @@ static int add_memory_block(unsigned long block_id, unsigned long state,
 
 static int __init add_boot_memory_block(unsigned long base_section_nr)
 {
-	int section_count = 0;
 	unsigned long nr;
 
-	for (nr = base_section_nr; nr < base_section_nr + sections_per_block;
-	     nr++)
-		if (present_section_nr(nr))
-			section_count++;
+	for_each_present_section_nr(base_section_nr, nr) {
+		if (nr >= (base_section_nr + sections_per_block))
+			break;
 
-	if (section_count == 0)
-		return 0;
-	return add_memory_block(memory_block_id(base_section_nr),
-				MEM_ONLINE, NULL,  NULL);
+		return add_memory_block(memory_block_id(base_section_nr),
+					MEM_ONLINE, NULL, NULL);
+	}
+
+	return 0;
 }
 
 static int add_hotplug_memory_block(unsigned long block_id,
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9540b41894da..0f6646da34d7 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -2097,6 +2097,11 @@ static inline unsigned long next_present_section_nr(unsigned long section_nr)
 	return -1;
 }
 
+#define for_each_present_section_nr(start, section_nr)		\
+	for (section_nr = next_present_section_nr(start - 1);	\
+	     section_nr != -1;					\
+	     section_nr = next_present_section_nr(section_nr))
+
 /*
  * These are _only_ used during initialisation, therefore they
  * can use __initdata ...  They could have names to indicate
diff --git a/mm/sparse.c b/mm/sparse.c
index 133b033d0cba..fe77d523ab8d 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -170,11 +170,6 @@ static void __section_mark_present(struct mem_section *ms,
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 }
 
-#define for_each_present_section_nr(start, section_nr)		\
-	for (section_nr = next_present_section_nr(start-1);	\
-	     section_nr != -1;								\
-	     section_nr = next_present_section_nr(section_nr))
-
 static inline unsigned long first_present_section_nr(void)
 {
 	return next_present_section_nr(-1);
-- 
2.48.1