powerpc/32: drop get_pteptr()

Commit 8d30c14c ("powerpc/mm: Rework I$/D$ coherency (v3)") and
commit 90ac19a8 ("[POWERPC] Abolish iopa(), mm_ptov(),
io_block_mapping() from arch/powerpc") removed the use of get_pteptr()
outside of mm/pgtable_32.c

In mm/pgtable_32.c, the only user of get_pteptr() is change_page_attr()
which operates on kernel context and on lowmem pages only.

Make virt_to_kpte() available outside of mm/mem.c and use it instead
of get_pteptr(), and drop get_pteptr()
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/788378c6c3ba5c5298caab7c7f95e6c3c88244b8.1578558199.git.christophe.leroy@c-s.fr

arch/powerpc/include/asm/pgtable.h

@@ -51,6 +51,11 @@ static inline pmd_t *pmd_ptr_k(unsigned long va)
 {
 	return pmd_offset(pud_offset(pgd_offset_k(va), va), va);
 }
+
+static inline pte_t *virt_to_kpte(unsigned long vaddr)
+{
+	return pte_offset_kernel(pmd_ptr_k(vaddr), vaddr);
+}
 #endif
 
 #include <asm/tlbflush.h>

arch/powerpc/mm/mem.c

@@ -66,11 +66,6 @@ pte_t *kmap_pte;
 EXPORT_SYMBOL(kmap_pte);
 pgprot_t kmap_prot;
 EXPORT_SYMBOL(kmap_prot);
-
-static inline pte_t *virt_to_kpte(unsigned long vaddr)
-{
-	return pte_offset_kernel(pmd_ptr_k(vaddr), vaddr);
-}
 #endif
 
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,

arch/powerpc/mm/pgtable_32.c

@@ -121,44 +121,9 @@ void __init mapin_ram(void)
 	}
 }
 
-/* Scan the real Linux page tables and return a PTE pointer for
- * a virtual address in a context.
- * Returns true (1) if PTE was found, zero otherwise.  The pointer to
- * the PTE pointer is unmodified if PTE is not found.
- */
-static int
-get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
-{
-        pgd_t	*pgd;
-	pud_t	*pud;
-        pmd_t	*pmd;
-        pte_t	*pte;
-        int     retval = 0;
-
-        pgd = pgd_offset(mm, addr & PAGE_MASK);
-        if (pgd) {
-		pud = pud_offset(pgd, addr & PAGE_MASK);
-		if (pud && pud_present(*pud)) {
-			pmd = pmd_offset(pud, addr & PAGE_MASK);
-			if (pmd_present(*pmd)) {
-				pte = pte_offset_map(pmd, addr & PAGE_MASK);
-				if (pte) {
-					retval = 1;
-					*ptep = pte;
-					if (pmdp)
-						*pmdp = pmd;
-					/* XXX caller needs to do pte_unmap, yuck */
-				}
-			}
-		}
-        }
-        return(retval);
-}
-
 static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
 {
 	pte_t *kpte;
-	pmd_t *kpmd;
 	unsigned long address;
 
 	BUG_ON(PageHighMem(page));
@@ -166,10 +131,10 @@ static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
 
 	if (v_block_mapped(address))
 		return 0;
-	if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
+	kpte = virt_to_kpte(address);
+	if (!kpte)
 		return -EINVAL;
 	__set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
-	pte_unmap(kpte);
 
 	return 0;
 }