[PATCH v2, part1 01/29] mm: introduce common help functions to deal with reserved/managed pages

[Jiang Liu <liuj97@gmail.com>]

Code to deal with reserved/managed pages are duplicated by many
architectures, so introduce common help functions to reduce duplicated
code. These common help functions will also be used to concentrate code
to modify totalram_pages and zone->managed_pages, which makes the code
much more clear.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
 include/linux/mm.h |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
 mm/page_alloc.c    |   20 ++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7acc9dc..d75c14b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1295,6 +1295,54 @@ extern void free_area_init_node(int nid, unsigned long * zones_size,
 		unsigned long zone_start_pfn, unsigned long *zholes_size);
 extern void free_initmem(void);
 
+/*
+ * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
+ * into the buddy system. The freed pages will be poisoned with pattern
+ * "poison" if it's non-zero.
+ * Return pages freed into the buddy system.
+ */
+extern unsigned long free_reserved_area(unsigned long start, unsigned long end,
+					int poison, char *s);
+
+static inline void adjust_managed_page_count(struct page *page, long count)
+{
+	totalram_pages += count;
+}
+
+/* Free the reserved page into the buddy system, so it gets managed. */
+static inline void __free_reserved_page(struct page *page)
+{
+	ClearPageReserved(page);
+	init_page_count(page);
+	__free_page(page);
+}
+
+static inline void free_reserved_page(struct page *page)
+{
+	__free_reserved_page(page);
+	adjust_managed_page_count(page, 1);
+}
+
+static inline void mark_page_reserved(struct page *page)
+{
+	SetPageReserved(page);
+	adjust_managed_page_count(page, -1);
+}
+
+/*
+ * Default method to free all the __init memory into the buddy system.
+ * The freed pages will be poisoned with pattern "poison" if it is
+ * non-zero. Return pages freed into the buddy system.
+ */
+static inline unsigned long free_initmem_default(int poison)
+{
+	extern char __init_begin[], __init_end[];
+
+	return free_reserved_area(PAGE_ALIGN((unsigned long)&__init_begin) ,
+				  ((unsigned long)&__init_end) & PAGE_MASK,
+				  poison, "unused kernel");
+}
+
 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
 /*
  * With CONFIG_HAVE_MEMBLOCK_NODE_MAP set, an architecture may initialise its
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8fcced7..0fadb09 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5113,6 +5113,26 @@ early_param("movablecore", cmdline_parse_movablecore);
 
 #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
 
+unsigned long free_reserved_area(unsigned long start, unsigned long end,
+				 int poison, char *s)
+{
+	unsigned long pages, pos;
+
+	pos = start = PAGE_ALIGN(start);
+	end &= PAGE_MASK;
+	for (pages = 0; pos < end; pos += PAGE_SIZE, pages++) {
+		if (poison)
+			memset((void *)pos, poison, PAGE_SIZE);
+		free_reserved_page(virt_to_page(pos));
+	}
+
+	if (pages && s)
+		pr_info("Freeing %s memory: %ldK (%lx - %lx)\n",
+			s, pages << (PAGE_SHIFT - 10), start, end);
+
+	return pages;
+}
+
 /**
  * set_dma_reserve - set the specified number of pages reserved in the first zone
  * @new_dma_reserve: The number of pages to mark reserved
-- 
1.7.9.5

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