mm/memory_hotplug: cleanup return value handing in do_migrate_range()

Return value mechanism of do_migrate_range() is not very simple, while no
caller of the function checks the return value.  Make the function return
nothing to be more simple, and cleanup related unnecessary code.

Link: https://lkml.kernel.org/r/20230216170703.64574-1-sj@kernel.org
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory_hotplug.c

@@ -1620,12 +1620,10 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
 	return 0;
 }
 
-static int
-do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
+static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 {
 	unsigned long pfn;
 	struct page *page, *head;
-	int ret = 0;
 	LIST_HEAD(source);
 	static DEFINE_RATELIMIT_STATE(migrate_rs, DEFAULT_RATELIMIT_INTERVAL,
 				      DEFAULT_RATELIMIT_BURST);
@@ -1679,7 +1677,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 						    page_is_file_lru(page));
 
 		} else {
-			ret = -EBUSY;
 			if (__ratelimit(&migrate_rs)) {
 				pr_warn("failed to isolate pfn %lx\n", pfn);
 				dump_page(page, "isolation failed");
@@ -1693,6 +1690,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			.nmask = &nmask,
 			.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
 		};
+		int ret;
 
 		/*
 		 * We have checked that migration range is on a single zone so
@@ -1721,8 +1719,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			putback_movable_pages(&source);
 		}
 	}
-
-	return ret;
 }
 
 static int __init cmdline_parse_movable_node(char *p)