[PATCH review for 4.9 22/50] mm/memory_hotplug: set magic number to page->freelist instead of page->lru.next

["Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com>]

From: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>

[ Upstream commit ddffe98d166f4a93d996d5aa628fd745311fc1e7 ]

To identify that pages of page table are allocated from bootmem
allocator, magic number sets to page->lru.next.

But page->lru list is initialized in reserve_bootmem_region().  So when
calling free_pagetable(), the function cannot find the magic number of
pages.  And free_pagetable() frees the pages by free_reserved_page() not
put_page_bootmem().

But if the pages are allocated from bootmem allocator and used as page
table, the pages have private flag.  So before freeing the pages, we
should clear the private flag by put_page_bootmem().

Before applying the commit 7bfec6f47bb0 ("mm, page_alloc: check multiple
page fields with a single branch"), we could find the following visible
issue:

  BUG: Bad page state in process kworker/u1024:1
  page:ffffea103cfd8040 count:0 mapcount:0 mappi
  flags: 0x6fffff80000800(private)
  page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
  bad because of flags: 0x800(private)
  <snip>
  Call Trace:
  [...] dump_stack+0x63/0x87
  [...] bad_page+0x114/0x130
  [...] free_pages_prepare+0x299/0x2d0
  [...] free_hot_cold_page+0x31/0x150
  [...] __free_pages+0x25/0x30
  [...] free_pagetable+0x6f/0xb4
  [...] remove_pagetable+0x379/0x7ff
  [...] vmemmap_free+0x10/0x20
  [...] sparse_remove_one_section+0x149/0x180
  [...] __remove_pages+0x2e9/0x4f0
  [...] arch_remove_memory+0x63/0xc0
  [...] remove_memory+0x8c/0xc0
  [...] acpi_memory_device_remove+0x79/0xa5
  [...] acpi_bus_trim+0x5a/0x8d
  [...] acpi_bus_trim+0x38/0x8d
  [...] acpi_device_hotplug+0x1b7/0x418
  [...] acpi_hotplug_work_fn+0x1e/0x29
  [...] process_one_work+0x152/0x400
  [...] worker_thread+0x125/0x4b0
  [...] kthread+0xd8/0xf0
  [...] ret_from_fork+0x22/0x40

And the issue still silently occurs.

Until freeing the pages of page table allocated from bootmem allocator,
the page->freelist is never used.  So the patch sets magic number to
page->freelist instead of page->lru.next.

[isimatu.yasuaki@jp.fujitsu.com: fix merge issue]
  Link: http://lkml.kernel.org/r/722b1cc4-93ac-dd8b-2be2-7a7e313b3b0b@gmail.com
Link: http://lkml.kernel.org/r/2c29bd9f-5b67-02d0-18a3-8828e78bbb6f@gmail.com
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
---
 arch/x86/mm/init_64.c | 2 +-
 mm/memory_hotplug.c   | 5 +++--
 mm/sparse.c           | 2 +-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 9a324fc8bed8..3e27ded6ac65 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -689,7 +689,7 @@ static void __meminit free_pagetable(struct page *page, int order)
 	if (PageReserved(page)) {
 		__ClearPageReserved(page);
 
-		magic = (unsigned long)page->lru.next;
+		magic = (unsigned long)page->freelist;
 		if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
 			while (nr_pages--)
 				put_page_bootmem(page++);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index ede137345a99..c9f715b2917f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -179,7 +179,7 @@ static void release_memory_resource(struct resource *res)
 void get_page_bootmem(unsigned long info,  struct page *page,
 		      unsigned long type)
 {
-	page->lru.next = (struct list_head *) type;
+	page->freelist = (void *)type;
 	SetPagePrivate(page);
 	set_page_private(page, info);
 	page_ref_inc(page);
@@ -189,11 +189,12 @@ void put_page_bootmem(struct page *page)
 {
 	unsigned long type;
 
-	type = (unsigned long) page->lru.next;
+	type = (unsigned long) page->freelist;
 	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
 	       type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
 
 	if (page_ref_dec_return(page) == 1) {
+		page->freelist = NULL;
 		ClearPagePrivate(page);
 		set_page_private(page, 0);
 		INIT_LIST_HEAD(&page->lru);
diff --git a/mm/sparse.c b/mm/sparse.c
index 1e168bf2779a..8c4c82e358e6 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -662,7 +662,7 @@ static void free_map_bootmem(struct page *memmap)
 		>> PAGE_SHIFT;
 
 	for (i = 0; i < nr_pages; i++, page++) {
-		magic = (unsigned long) page->lru.next;
+		magic = (unsigned long) page->freelist;
 
 		BUG_ON(magic == NODE_INFO);
 
-- 
2.11.0