[PATCH v6 3/4] x86/mm/pat: Convert populate_pgd() to use page table apis

[Vishal Moola (Oracle)]

We need all allocation and free sites to use the ptdesc APIs in order to
allocate them separately from regular pages. Convert the remaining
get_zeroed_page() calls to the generic page table apis, since those
use ptdescs already.

Pass through init_mm since these are kernel page tables, both functions
need it to identify kernel page tables. Also, the generic
implementations don't use the second argument. Pass it a placeholder so
we don't have to reimplement it or risk breaking other architectures.

Its not obvious if these pages get freed. Regardless, the only other
possible free paths have already been converted, and my frozen page
table test kernel hasn't found any issues.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
---
 arch/x86/mm/pat/set_memory.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 655bef618ea0..8f74d4bfd591 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1746,7 +1746,11 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	pgd_entry = cpa->pgd + pgd_index(addr);
 
 	if (pgd_none(*pgd_entry)) {
-		p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);
+		/* The generic implementation of p4d_alloc_one()
+		 * doesn't use the second argument. Pass it 0 as
+		 * a placeholder.
+		 */
+		p4d = p4d_alloc_one(&init_mm, 0);
 		if (!p4d)
 			return -1;
 
@@ -1758,7 +1762,11 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	 */
 	p4d = p4d_offset(pgd_entry, addr);
 	if (p4d_none(*p4d)) {
-		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
+		/* The generic implementation of pud_alloc_one()
+		 * doesn't use the second argument. Pass it 0 as
+		 * a placeholder.
+		 */
+		pud = pud_alloc_one(&init_mm, 0);
 		if (!pud)
 			return -1;
 
-- 
2.53.0