1 files changed, 15 insertions, 14 deletions

diff --git a/mm/sparse.c b/mm/sparse.c
index b20ab7cdac867..aadb7298dcefd 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -198,16 +198,6 @@ static void section_mark_present(struct mem_section *ms)
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 }
 
-static inline unsigned long next_present_section_nr(unsigned long section_nr)
-{
-	do {
-		section_nr++;
-		if (present_section_nr(section_nr))
-			return section_nr;
-	} while ((section_nr <= __highest_present_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) &&				\
@@ -744,6 +734,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	struct mem_section *ms = __pfn_to_section(pfn);
 	bool section_is_early = early_section(ms);
 	struct page *memmap = NULL;
+	bool empty;
 	unsigned long *subsection_map = ms->usage
 		? &ms->usage->subsection_map[0] : NULL;
 
@@ -774,21 +765,31 @@ 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)) {
+	empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
+	if (empty) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
-		if (!section_is_early) {
+		/*
+		 * When removing an early section, the usage map is kept (as the
+		 * usage maps of other sections fall into the same page). It
+		 * will be re-used when re-adding the section - which is then no
+		 * longer an early section. If the usage map is PageReserved, it
+		 * was allocated during boot.
+		 */
+		if (!PageReserved(virt_to_page(ms->usage))) {
 			kfree(ms->usage);
 			ms->usage = NULL;
 		}
 		memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
-		ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr);
 	}
 
 	if (section_is_early && memmap)
 		free_map_bootmem(memmap);
 	else
 		depopulate_section_memmap(pfn, nr_pages, altmap);
+
+	if (empty)
+		ms->section_mem_map = (unsigned long)NULL;
 }
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
@@ -879,7 +880,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 	 * Poison uninitialized struct pages in order to catch invalid flags
 	 * combinations.
 	 */
-	page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages);
+	page_init_poison(memmap, sizeof(struct page) * nr_pages);
 
 	ms = __nr_to_section(section_nr);
 	set_section_nid(section_nr, nid);