[PATCH v6, part3 12/16] mm: make __free_pages_bootmem() only available at boot time

[Jiang Liu]

In order to simpilify management of totalram_pages and
zone->managed_pages, make __free_pages_bootmem() only available
at boot time. With this change applied, __free_pages_bootmem()
will only be used by bootmem.c and nobootmem.c at boot time,
so mark it as __init.  Other callers of __free_pages_bootmem()
have been converted to use free_reserved_page(), which handles
totalram_pages and zone->managed_pages in a safer way.

This patch also fix a bug in free_pagetable() for x86_64, which
should increase zone->managed_pages instead of zone->present_pages
when freeing reserved pages.

And now we have managed_pages_count_lock to protect totalram_pages
and zone->managed_pages, so remove the redundant ppb_lock lock in
put_page_bootmem(). This greatly simplifies the locking rules.

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: Wen Congyang <wency@xxxxxxxxxxxxxx>
Cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
---
 arch/x86/mm/init_64.c | 18 ++----------------
 mm/memory_hotplug.c   | 16 ++--------------
 mm/page_alloc.c       |  9 +--------
 3 files changed, 5 insertions(+), 38 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 32e2f25..3bdf32b 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -712,36 +712,22 @@ EXPORT_SYMBOL_GPL(arch_add_memory);
 
 static void __meminit free_pagetable(struct page *page, int order)
 {
-	struct zone *zone;
-	bool bootmem = false;
 	unsigned long magic;
 	unsigned int nr_pages = 1 << order;
 
 	/* bootmem page has reserved flag */
 	if (PageReserved(page)) {
 		__ClearPageReserved(page);
-		bootmem = true;
 
 		magic = (unsigned long)page->lru.next;
 		if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
 			while (nr_pages--)
 				put_page_bootmem(page++);
 		} else
-			__free_pages_bootmem(page, order);
+			while (nr_pages--)
+				free_reserved_page(page++);
 	} else
 		free_pages((unsigned long)page_address(page), order);
-
-	/*
-	 * SECTION_INFO pages and MIX_SECTION_INFO pages
-	 * are all allocated by bootmem.
-	 */
-	if (bootmem) {
-		zone = page_zone(page);
-		zone_span_writelock(zone);
-		zone->present_pages += nr_pages;
-		zone_span_writeunlock(zone);
-		totalram_pages += nr_pages;
-	}
 }
 
 static void __meminit free_pte_table(pte_t *pte_start, pmd_t *pmd)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 037d41d..c291295 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -101,12 +101,9 @@ void get_page_bootmem(unsigned long info,  struct page *page,
 	atomic_inc(&page->_count);
 }
 
-/* reference to __meminit __free_pages_bootmem is valid
- * so use __ref to tell modpost not to generate a warning */
-void __ref put_page_bootmem(struct page *page)
+void put_page_bootmem(struct page *page)
 {
 	unsigned long type;
-	static DEFINE_MUTEX(ppb_lock);
 
 	type = (unsigned long) page->lru.next;
 	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
@@ -116,17 +113,8 @@ void __ref put_page_bootmem(struct page *page)
 		ClearPagePrivate(page);
 		set_page_private(page, 0);
 		INIT_LIST_HEAD(&page->lru);
-
-		/*
-		 * Please refer to comment for __free_pages_bootmem()
-		 * for why we serialize here.
-		 */
-		mutex_lock(&ppb_lock);
-		__free_pages_bootmem(page, 0);
-		mutex_unlock(&ppb_lock);
-		totalram_pages++;
+		free_reserved_page(page);
 	}
-
 }
 
 #ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 14117a2..a07e70a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -745,14 +745,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 	local_irq_restore(flags);
 }
 
-/*
- * Read access to zone->managed_pages is safe because it's unsigned long,
- * but we still need to serialize writers. Currently all callers of
- * __free_pages_bootmem() except put_page_bootmem() should only be used
- * at boot time. So for shorter boot time, we shift the burden to
- * put_page_bootmem() to serialize writers.
- */
-void __meminit __free_pages_bootmem(struct page *page, unsigned int order)
+void __init __free_pages_bootmem(struct page *page, unsigned int order)
 {
 	unsigned int nr_pages = 1 << order;
 	unsigned int loop;
-- 
1.8.1.2

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