powerpc: Replace mem_init_done with slab_is_available()

We have a powerpc specific global called mem_init_done which is "set on
boot once kmalloc can be called".

But that's not *quite* true. We set it at the bottom of mem_init(), and
rely on the fact that mm_init() calls kmem_cache_init() immediately
after that, and nothing is running in parallel.

So replace it with the generic and 100% correct slab_is_available().

Signed-off-by: Michael Ellerman <[e-mail]>

arch/powerpc/include/asm/setup.h

···
 extern void ppc_printk_progress(char *s, unsigned short hex);
 
 extern unsigned int rtas_data;
-extern int mem_init_done;	/* set on boot once kmalloc can be called */
 extern unsigned long long memory_limit;
 extern unsigned long klimit;
 extern void *zalloc_maybe_bootmem(size_t size, gfp_t mask);

arch/powerpc/kernel/pci-common.c

···
 	list_add_tail(&phb->list_node, &hose_list);
 	spin_unlock(&hose_spinlock);
 	phb->dn = dev;
-	phb->is_dynamic = mem_init_done;
+	phb->is_dynamic = slab_is_available();
 #ifdef CONFIG_PPC64
 	if (dev) {
 		int nid = of_node_to_nid(dev);

arch/powerpc/kernel/rtas.c

···
 			buf = altbuf;
 		} else {
 			buf = rtas_err_buf;
-			if (mem_init_done)
+			if (slab_is_available())
 				buf = kmalloc(RTAS_ERROR_LOG_MAX, GFP_ATOMIC);
 		}
 		if (buf)
···
 
 	if (buff_copy) {
 		log_error(buff_copy, ERR_TYPE_RTAS_LOG, 0);
-		if (mem_init_done)
+		if (slab_is_available())
 			kfree(buff_copy);
 	}
 	return ret;

arch/powerpc/lib/alloc.c

···
 {
 	void *p;
 
-	if (mem_init_done)
+	if (slab_is_available())
 		p = kzalloc(size, mask);
 	else {
 		p = memblock_virt_alloc(size, 0);

arch/powerpc/mm/mem.c

···
 #define CPU_FTR_NOEXECUTE	0
 #endif
 
-int mem_init_done;
 unsigned long long memory_limit;
 
 #ifdef CONFIG_HIGHMEM
···
 	pr_info("  * 0x%08lx..0x%08lx  : vmalloc & ioremap\n",
 		VMALLOC_START, VMALLOC_END);
 #endif /* CONFIG_PPC32 */
-
-	mem_init_done = 1;
 }
 
 void free_initmem(void)

arch/powerpc/mm/pgtable_32.c

···
 __init_refok pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 {
 	pte_t *pte;
-	extern int mem_init_done;
 
-	if (mem_init_done) {
+	if (slab_is_available()) {
 		pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);
 	} else {
 		pte = __va(memblock_alloc(PAGE_SIZE, PAGE_SIZE));
···
 	 * Don't allow anybody to remap normal RAM that we're using.
 	 * mem_init() sets high_memory so only do the check after that.
 	 */
-	if (mem_init_done && (p < virt_to_phys(high_memory)) &&
+	if (slab_is_available() && (p < virt_to_phys(high_memory)) &&
 	    !(__allow_ioremap_reserved && memblock_is_region_reserved(p, size))) {
 		printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
 		       (unsigned long long)p, __builtin_return_address(0));
···
 	if ((v = p_mapped_by_tlbcam(p)))
 		goto out;
 
-	if (mem_init_done) {
+	if (slab_is_available()) {
 		struct vm_struct *area;
 		area = get_vm_area_caller(size, VM_IOREMAP, caller);
 		if (area == 0)
···
 	for (i = 0; i < size && err == 0; i += PAGE_SIZE)
 		err = map_page(v+i, p+i, flags);
 	if (err) {
-		if (mem_init_done)
+		if (slab_is_available())
 			vunmap((void *)v);
 		return NULL;
 	}

arch/powerpc/mm/pgtable_64.c

···
 	if ((size == 0) || (paligned == 0))
 		return NULL;
 
-	if (mem_init_done) {
+	if (slab_is_available()) {
 		struct vm_struct *area;
 
 		area = __get_vm_area_caller(size, VM_IOREMAP,
···
 {
 	void *addr;
 
-	if (!mem_init_done)
+	if (!slab_is_available())
 		return;
 	
 	addr = (void *) ((unsigned long __force)