[PATCH] mm: fix huge page table not free after memory unplug

[Yuan Liu <yuan1.liu@intel.com>]

newly plugged memory is marked as prot_sethuge via phys_pmd_init
without setting PG_head. During memory unplug, free_hugepage_table
frees the page table as 2M, but pagetable_free handles it as 4K.

The following test case of memory unplug for a VM [1], tested in
the environment [2], show that results.

+-----------------------+------+------+
|Check System Memory    |Plug  |Unplug|
|via free -h            |256GB |256GB |
+-----------------------+------+------+
| Free 4K page table    |257GB |5.6GB |
+-----------------------+------+------+
| Free 2M page table    |257GB |1.7GB |
+-----------------------+------+------+

[1] Qemu commands to unhotplug 256G memory for a VM:
    object_add memory-backend-ram,id=hotmem0,size=256G,share=on
    device_add virtio-mem-pci,id=vmem1,memdev=hotmem0,bus=port1
    qom-set vmem1 requested-size 256G (Plug Memory)
    qom-set vmem1 requested-size 0G (Unplug Memory)

[2] Hardware     : Intel Icelake server
    Guest Kernel : v6.19-rc1
    Qemu         : v9.0.0

Launch VM:
    qemu-system-x86_64 -accel kvm -cpu host \
    -drive file=./Centos10_cloud.qcow2,format=qcow2,if=virtio \
    -drive file=./seed.img,format=raw,if=virtio \
    -smp 3,cores=3,threads=1,sockets=1,maxcpus=3 \
    -m 2G,slots=10,maxmem=2052472M \
    -device pcie-root-port,id=port1,bus=pcie.0,slot=1,multifunction=on \
    -device pcie-root-port,id=port2,bus=pcie.0,slot=2 \
    -nographic -machine q35 \
    -nic user,hostfwd=tcp::3000-:22

   Guest kernel auto-onlines newly added memory blocks:
   echo online > /sys/devices/system/memory/auto_online_blocks

Signed-off-by: Yuan Liu <yuan1.liu@intel.com>
---
 arch/x86/mm/init_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 9983017ecbe0..1044aafd5d94 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1028,7 +1028,7 @@ static void __meminit free_pagetable(struct page *page, int order)
 		free_reserved_pages(page, nr_pages);
 #endif
 	} else {
-		pagetable_free(page_ptdesc(page));
+		__free_pages(page, order);
 	}
 }
 
-- 
2.47.3