[PATCH V2] mm: fix node spanned pages when we have a node with only zone_movable

[Linxu Fang <fanglinxu@huawei.com>]

commit <342332e6a925> ("mm/page_alloc.c: introduce kernelcore=mirror
option") and series patches rewrote the calculation of node spanned
pages.
commit <e506b99696a2> (mem-hotplug: fix node spanned pages when we have a
movable node), but the current code still has problems,
when we have a node with only zone_movable and the node id is not zero,
the size of node spanned pages is double added.
That's because we have an empty normal zone, and zone_start_pfn or
zone_end_pfn is not between arch_zone_lowest_possible_pfn and
arch_zone_highest_possible_pfn, so we need to use clamp to constrain the
range just like the commit <96e907d13602> (bootmem: Reimplement
__absent_pages_in_range() using for_each_mem_pfn_range()).

e.g.
Zone ranges:
  DMA      [mem 0x0000000000001000-0x0000000000ffffff]
  DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
  Normal   [mem 0x0000000100000000-0x000000023fffffff]
Movable zone start for each node
  Node 0: 0x0000000100000000
  Node 1: 0x0000000140000000
Early memory node ranges
  node   0: [mem 0x0000000000001000-0x000000000009efff]
  node   0: [mem 0x0000000000100000-0x00000000bffdffff]
  node   0: [mem 0x0000000100000000-0x000000013fffffff]
  node   1: [mem 0x0000000140000000-0x000000023fffffff]

node 0 DMA	spanned:0xfff   present:0xf9e   absent:0x61
node 0 DMA32	spanned:0xff000 present:0xbefe0	absent:0x40020
node 0 Normal	spanned:0	present:0	absent:0
node 0 Movable	spanned:0x40000 present:0x40000 absent:0
On node 0 totalpages(node_present_pages): 1048446
node_spanned_pages:1310719
node 1 DMA	spanned:0	    present:0		absent:0
node 1 DMA32	spanned:0	    present:0		absent:0
node 1 Normal	spanned:0x100000    present:0x100000	absent:0
node 1 Movable	spanned:0x100000    present:0x100000	absent:0
On node 1 totalpages(node_present_pages): 2097152
node_spanned_pages:2097152
Memory: 6967796K/12582392K available (16388K kernel code, 3686K rwdata,
4468K rodata, 2160K init, 10444K bss, 5614596K reserved, 0K
cma-reserved)

It shows that the current memory of node 1 is double added.
After this patch, the problem is fixed.

node 0 DMA	spanned:0xfff   present:0xf9e   absent:0x61
node 0 DMA32	spanned:0xff000 present:0xbefe0	absent:0x40020
node 0 Normal	spanned:0	present:0	absent:0
node 0 Movable	spanned:0x40000 present:0x40000 absent:0
On node 0 totalpages(node_present_pages): 1048446
node_spanned_pages:1310719
node 1 DMA	spanned:0	    present:0		absent:0
node 1 DMA32	spanned:0	    present:0		absent:0
node 1 Normal	spanned:0	    present:0		absent:0
node 1 Movable	spanned:0x100000    present:0x100000	absent:0
On node 1 totalpages(node_present_pages): 1048576
node_spanned_pages:1048576
memory: 6967796K/8388088K available (16388K kernel code, 3686K rwdata,
4468K rodata, 2160K init, 10444K bss, 1420292K reserved, 0K
cma-reserved)

Signed-off-by: Linxu Fang <fanglinxu@huawei.com>
---
 mm/page_alloc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3eb01de..5cd0cb2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6233,13 +6233,15 @@ static unsigned long __init zone_spanned_pages_in_node(int nid,
 					unsigned long *zone_end_pfn,
 					unsigned long *ignored)
 {
+	unsigned long zone_low = arch_zone_lowest_possible_pfn[zone_type];
+	unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
 	/* When hotadd a new node from cpu_up(), the node should be empty */
 	if (!node_start_pfn && !node_end_pfn)
 		return 0;
 
 	/* Get the start and end of the zone */
-	*zone_start_pfn = arch_zone_lowest_possible_pfn[zone_type];
-	*zone_end_pfn = arch_zone_highest_possible_pfn[zone_type];
+	*zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
+	*zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
 	adjust_zone_range_for_zone_movable(nid, zone_type,
 				node_start_pfn, node_end_pfn,
 				zone_start_pfn, zone_end_pfn);
-- 
1.8.5.6