s390: make setup_zero_pages() use memblock

Allocating the zero pages from memblock is simpler because the memory is
already reserved.

This will also help with pulling out memblock_free_all() to the generic
code and reducing code duplication in arch::mem_init().

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Mike Rapoport (Microsoft) <[e-mail]>
Acked-by: Heiko Carstens <[e-mail]>
Cc: Alexander Gordeev <[e-mail]>
Cc: Andreas Larsson <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Ard Biesheuvel <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Borislav Betkov <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Dinh Nguyen <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Gerald Schaefer <[e-mail]>
Cc: Guo Ren (csky) <[e-mail]>
Cc: Helge Deller <[e-mail]>
Cc: Huacai Chen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiaxun Yang <[e-mail]>
Cc: Johannes Berg <[e-mail]>
Cc: John Paul Adrian Glaubitz <[e-mail]>
Cc: Madhavan Srinivasan <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Matt Turner <[e-mail]>
Cc: Max Filippov <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Michal Simek <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Richard Weinberger <[e-mail]>
Cc: Russel King <[e-mail]>
Cc: Stafford Horne <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Thomas Gleinxer <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Cc: Vineet Gupta <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/s390/mm/init.c

···
 {
 	unsigned long total_pages = memblock_estimated_nr_free_pages();
 	unsigned int order;
-	struct page *page;
-	int i;
 
 	/* Latest machines require a mapping granularity of 512KB */
 	order = 7;
···
 	while (order > 2 && (total_pages >> 10) < (1UL << order))
 		order--;
 
-	empty_zero_page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
-	if (!empty_zero_page)
-		panic("Out of memory in setup_zero_pages");
-
-	page = virt_to_page((void *) empty_zero_page);
-	split_page(page, order);
-	for (i = 1 << order; i > 0; i--) {
-		mark_page_reserved(page);
-		page++;
-	}
+	empty_zero_page = (unsigned long)memblock_alloc_or_panic(PAGE_SIZE << order, PAGE_SIZE);
 
 	zero_page_mask = ((PAGE_SIZE << order) - 1) & PAGE_MASK;
 }
···
 	pv_init();
 	kfence_split_mapping();
 
+	setup_zero_pages();	/* Setup zeroed pages. */
+
 	/* this will put all low memory onto the freelists */
 	memblock_free_all();
-	setup_zero_pages();	/* Setup zeroed pages. */
 }
 
 unsigned long memory_block_size_bytes(void)