powerpc/kasan: Remove unnecessary page table locking

Commit 45ff3c55 ("powerpc/kasan: Fix parallel loading of
modules.") added spinlocks to manage parallele module loading.

Since then commit 47febbee ("powerpc/32: Force KASAN_VMALLOC for
modules") converted the module loading to KASAN_VMALLOC.

The spinlocking has then become unneeded and can be removed to
simplify kasan_init_shadow_page_tables()

Also remove inclusion of linux/moduleloader.h and linux/vmalloc.h
which are not needed anymore since the removal of modules management.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/81a4d3aee8b82bc1355595935c8f4ad9d3b22a83.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/mm/kasan/kasan_init_32.c

@@ -5,9 +5,7 @@
 #include <linux/kasan.h>
 #include <linux/printk.h>
 #include <linux/memblock.h>
-#include <linux/moduleloader.h>
 #include <linux/sched/task.h>
-#include <linux/vmalloc.h>
 #include <asm/pgalloc.h>
 #include <asm/code-patching.h>
 #include <mm/mmu_decl.h>
@@ -34,31 +32,22 @@ static int __init kasan_init_shadow_page_tables(unsigned long k_start, unsigned
 {
 	pmd_t *pmd;
 	unsigned long k_cur, k_next;
-	pte_t *new = NULL;
 
 	pmd = pmd_ptr_k(k_start);
 
 	for (k_cur = k_start; k_cur != k_end; k_cur = k_next, pmd++) {
+		pte_t *new;
+
 		k_next = pgd_addr_end(k_cur, k_end);
 		if ((void *)pmd_page_vaddr(*pmd) != kasan_early_shadow_pte)
 			continue;
 
-		if (!new)
-			new = memblock_alloc(PTE_FRAG_SIZE, PTE_FRAG_SIZE);
+		new = memblock_alloc(PTE_FRAG_SIZE, PTE_FRAG_SIZE);
 
 		if (!new)
 			return -ENOMEM;
 		kasan_populate_pte(new, PAGE_KERNEL);
-
-		smp_wmb(); /* See comment in __pte_alloc */
-
-		spin_lock(&init_mm.page_table_lock);
-			/* Has another populated it ? */
-		if (likely((void *)pmd_page_vaddr(*pmd) == kasan_early_shadow_pte)) {
-			pmd_populate_kernel(&init_mm, pmd, new);
-			new = NULL;
-		}
-		spin_unlock(&init_mm.page_table_lock);
+		pmd_populate_kernel(&init_mm, pmd, new);
 	}
 	return 0;
 }