[PATCH 2/7] mm/sparse.c: Introduce a new function clear_subsection_map()

[Baoquan He <bhe@xxxxxxxxxx>]

Wrap the codes clearing subsection map of one memory region in
section_deactivate() into clear_subsection_map().

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
---
 mm/sparse.c | 44 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 37 insertions(+), 7 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 9ad741ccbeb6..696f6b9f706e 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -726,14 +726,25 @@ 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)
+/**
+ * clear_subsection_map - Clear subsection map of one memory region
+ *
+ * @pfn - start pfn of the memory range
+ * @nr_pages - number of pfns to add in the region
+ *
+ * This is only intended for hotplug, and clear the related subsection
+ * map inside one section.
+ *
+ * Return:
+ * * -EINVAL	- Section already deactived.
+ * * 0		- Subsection map is emptied.
+ * * 1		- Subsection map is not empty.
+ */
+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;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 
@@ -744,8 +755,28 @@ 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;
+		return -EINVAL;
+
+	bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
 
+	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
+		return 0;
+
+	return 1;
+}
+
+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;
+	int rc;
+
+
+	rc = clear_subsection_map(pfn, nr_pages);
+	if(IS_ERR_VALUE((unsigned long)rc))
+		return;
 	/*
 	 * There are 3 cases to handle across two configurations
 	 * (SPARSEMEM_VMEMMAP={y,n}):
@@ -763,8 +794,7 @@ 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);
-	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
+	if (!rc) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
 		/*
-- 
2.17.2