[PATCH v2 09/15] mm/sparse: remove sparse_decode_mem_map()

From: "David Hildenbrand (Arm)" <david@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	 Oscar Salvador <osalvador@suse.de>,
	 Axel Rasmussen <axelrasmussen@google.com>,
	Yuanchu Xie <yuanchu@google.com>,  Wei Xu <weixugc@google.com>,
	Lorenzo Stoakes <ljs@kernel.org>,
	 "Liam R. Howlett" <Liam.Howlett@oracle.com>,
	 Vlastimil Babka <vbabka@kernel.org>,
	Mike Rapoport <rppt@kernel.org>,
	 Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>,
	 Sidhartha Kumar <sidhartha.kumar@oracle.com>,
	linux-mm@kvack.org,  linux-cxl@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	 "David Hildenbrand (Arm)" <david@kernel.org>
Subject: [PATCH v2 09/15] mm/sparse: remove sparse_decode_mem_map()
Date: Fri, 20 Mar 2026 23:13:41 +0100	[thread overview]
Message-ID: <20260320-sparsemem_cleanups-v2-9-096addc8800d@kernel.org> (raw)
In-Reply-To: <20260320-sparsemem_cleanups-v2-0-096addc8800d@kernel.org>

section_deactivate() applies to CONFIG_SPARSEMEM_VMEMMAP only. So we can
just use pfn_to_page() (after making sure we have the start PFN of the
section), and remove sparse_decode_mem_map().

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 include/linux/memory_hotplug.h |  2 --
 mm/sparse.c                    | 16 +---------------
 2 files changed, 1 insertion(+), 17 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index e77ef3d7ff73..815e908c4135 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -308,8 +308,6 @@ extern int sparse_add_section(int nid, unsigned long pfn,
 		struct dev_pagemap *pgmap);
 extern void sparse_remove_section(unsigned long pfn, unsigned long nr_pages,
 				  struct vmem_altmap *altmap);
-extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
-					  unsigned long pnum);
 extern struct zone *zone_for_pfn_range(enum mmop online_type,
 		int nid, struct memory_group *group, unsigned long start_pfn,
 		unsigned long nr_pages);
diff --git a/mm/sparse.c b/mm/sparse.c
index 875f718a4c79..b5825c9ee2f2 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -274,18 +274,6 @@ static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long p
 	return coded_mem_map;
 }
 
-#ifdef CONFIG_MEMORY_HOTPLUG
-/*
- * Decode mem_map from the coded memmap
- */
-struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
-{
-	/* mask off the extra low bits of information */
-	coded_mem_map &= SECTION_MAP_MASK;
-	return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
-}
-#endif /* CONFIG_MEMORY_HOTPLUG */
-
 static void __meminit sparse_init_one_section(struct mem_section *ms,
 		unsigned long pnum, struct page *mem_map,
 		struct mem_section_usage *usage, unsigned long flags)
@@ -754,8 +742,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 
 	empty = is_subsection_map_empty(ms);
 	if (empty) {
-		unsigned long section_nr = pfn_to_section_nr(pfn);
-
 		/*
 		 * Mark the section invalid so that valid_section()
 		 * return false. This prevents code from dereferencing
@@ -774,7 +760,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 			kfree_rcu(ms->usage, rcu);
 			WRITE_ONCE(ms->usage, NULL);
 		}
-		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
+		memmap = pfn_to_page(SECTION_ALIGN_DOWN(pfn));
 	}
 
 	/*

-- 
2.43.0

