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Subject[RFC PATCH v1 31/33] mm: avoid using __free_pages_bootmem() at runtime
Date
Avoid using __free_pages_bootmem() at runtime, so we could easily
manage totalram_pages and zone->managed_pages. With this change applied,
__free_pages_bootmem() is only used by bootmem.c and nobootmem.c at
boot time, so mark it as __init. And other callers of
__free_pages_bootmem() have been switched to free_reserved_page(),
which handles totalram_pages and zone->managed_pages in a common 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 free_reserved_page() protects totalram_pages and zone->managed_pages
with managed_pages_count_lock, so remove the redundant ppb_lock lock in
put_page_bootmem(). This makes the locking rules much more clear.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: x86@kernel.org
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
---
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 474e28f..17cfe98 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -711,36 +711,22 @@ 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 b81a367b..af9e87f 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 2692931..d252443 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -741,14 +741,7 @@ 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;
--
1.7.9.5


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