linux-kernel - [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection

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Message-Id: <20200307084229.28251-4-bhe@redhat.com>
Date:   Sat,  7 Mar 2020 16:42:25 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, mhocko@...e.com,
        david@...hat.com, richardw.yang@...ux.intel.com,
        dan.j.williams@...el.com, osalvador@...e.de, rppt@...ux.ibm.com,
        bhe@...hat.com
Subject: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

Factor out the code which clear subsection map of one memory region from
section_deactivate() into clear_subsection_map().

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 mm/sparse.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index e37c0abcdc89..d9dcd58d5c1d 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
-		struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
 	DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
 	struct mem_section *ms = __pfn_to_section(pfn);
-	bool section_is_early = early_section(ms);
-	struct page *memmap = NULL;
-	bool empty = false;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 
@@ -745,8 +741,31 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
 				"section already deactivated (%#lx + %ld)\n",
 				pfn, nr_pages))
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return bitmap_empty(&ms->usage->subsection_map[0],
+			    SUBSECTIONS_PER_SECTION);
+}
+
+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
+		struct vmem_altmap *altmap)
+{
+	struct mem_section *ms = __pfn_to_section(pfn);
+	bool section_is_early = early_section(ms);
+	struct page *memmap = NULL;
+	bool empty = false;
+
+	if (clear_subsection_map(pfn, nr_pages))
 		return;
 
+	empty = is_subsection_map_empty(ms);
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):
@@ -764,8 +783,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	 *
 	 * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
 	 */
-	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
-	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
 	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
-- 
2.17.2