mm: introduce memmap_alloc() to unify memory map allocation

There are several places that allocate memory for the memory map:
alloc_node_mem_map() for FLATMEM, sparse_buffer_init() and
__populate_section_memmap() for SPARSEMEM.

The memory allocated in the FLATMEM case is zeroed and it is never
poisoned, regardless of CONFIG_PAGE_POISON setting.

The memory allocated in the SPARSEMEM cases is not zeroed and it is
implicitly poisoned inside memblock if CONFIG_PAGE_POISON is set.

Introduce memmap_alloc() wrapper for memblock allocators that will be used
for both FLATMEM and SPARSEMEM cases and will makei memory map zeroing and
poisoning consistent for different memory models.

Link: https://lkml.kernel.org/r/20210714123739.16493-4-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/internal.h

@@ -211,6 +211,10 @@ extern void zone_pcp_reset(struct zone *zone);
 extern void zone_pcp_disable(struct zone *zone);
 extern void zone_pcp_enable(struct zone *zone);
 
+extern void *memmap_alloc(phys_addr_t size, phys_addr_t align,
+			  phys_addr_t min_addr,
+			  int nid, bool exact_nid);
+
 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
 
 /*

mm/page_alloc.c

@@ -6748,6 +6748,26 @@ static void __init memmap_init(void)
 		init_unavailable_range(hole_pfn, end_pfn, zone_id, nid);
 }
 
+void __init *memmap_alloc(phys_addr_t size, phys_addr_t align,
+			  phys_addr_t min_addr, int nid, bool exact_nid)
+{
+	void *ptr;
+
+	if (exact_nid)
+		ptr = memblock_alloc_exact_nid_raw(size, align, min_addr,
+						   MEMBLOCK_ALLOC_ACCESSIBLE,
+						   nid);
+	else
+		ptr = memblock_alloc_try_nid_raw(size, align, min_addr,
+						 MEMBLOCK_ALLOC_ACCESSIBLE,
+						 nid);
+
+	if (ptr && size > 0)
+		page_init_poison(ptr, size);
+
+	return ptr;
+}
+
 static int zone_batchsize(struct zone *zone)
 {
 #ifdef CONFIG_MMU
@@ -7519,8 +7539,8 @@ static void __ref alloc_node_mem_map(struct pglist_data *pgdat)
 		end = pgdat_end_pfn(pgdat);
 		end = ALIGN(end, MAX_ORDER_NR_PAGES);
 		size =  (end - start) * sizeof(struct page);
-		map = memblock_alloc_node(size, SMP_CACHE_BYTES,
-					  pgdat->node_id);
+		map = memmap_alloc(size, SMP_CACHE_BYTES, MEMBLOCK_LOW_LIMIT,
+				   pgdat->node_id, false);
 		if (!map)
 			panic("Failed to allocate %ld bytes for node %d memory map\n",
 			      size, pgdat->node_id);

mm/sparse.c

@@ -436,8 +436,7 @@ struct page __init *__populate_section_memmap(unsigned long pfn,
 	if (map)
 		return map;
 
-	map = memblock_alloc_try_nid_raw(size, size, addr,
-					  MEMBLOCK_ALLOC_ACCESSIBLE, nid);
+	map = memmap_alloc(size, size, addr, nid, false);
 	if (!map)
 		panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n",
 		      __func__, size, PAGE_SIZE, nid, &addr);
@@ -464,8 +463,7 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
 	 * and we want it to be properly aligned to the section size - this is
 	 * especially the case for VMEMMAP which maps memmap to PMDs
 	 */
-	sparsemap_buf = memblock_alloc_exact_nid_raw(size, section_map_size(),
-					addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
+	sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true);
 	sparsemap_buf_end = sparsemap_buf + size;
 }