x86: pgtable: always use pte_free_kernel()

Page table pages are normally freed using the appropriate helper for the
given page table level. On x86, pud_free_pmd_page() and
pmd_free_pte_page() are an exception to the rule: they call free_page()
directly.

Constructor/destructor calls are about to be introduced for kernel PTEs.
To avoid missing dtor calls in those helpers, free the PTE pages using
pte_free_kernel() instead of free_page().

While at it also use pmd_free() instead of calling pagetable_dtor()
explicitly at the PMD level.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kevin Brodsky <[e-mail]>
Acked-by: Dave Hansen <[e-mail]>
Cc: Albert Ou <[e-mail]>
Cc: Andreas Larsson <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Linus Waleij <[e-mail]>
Cc: Madhavan Srinivasan <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Matthew Wilcox (Oracle) <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Qi Zheng <[e-mail]>
Cc: Ryan Roberts <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: <[e-mail]>
Cc: Yang Shi <[e-mail]>
Cc: Alexander Gordeev <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/x86/mm/pgtable.c

···
 	for (i = 0; i < PTRS_PER_PMD; i++) {
 		if (!pmd_none(pmd_sv[i])) {
 			pte = (pte_t *)pmd_page_vaddr(pmd_sv[i]);
-			free_page((unsigned long)pte);
+			pte_free_kernel(&init_mm, pte);
 		}
 	}
 
 	free_page((unsigned long)pmd_sv);
 
-	pagetable_dtor(virt_to_ptdesc(pmd));
-	free_page((unsigned long)pmd);
+	pmd_free(&init_mm, pmd);
 
 	return 1;
 }
···
 	/* INVLPG to clear all paging-structure caches */
 	flush_tlb_kernel_range(addr, addr + PAGE_SIZE-1);
 
-	free_page((unsigned long)pte);
+	pte_free_kernel(&init_mm, pte);
 
 	return 1;
 }