mm/memory_hotplug: rate limit page migration warnings

When offlining memory the system can attempt to migrate a lot of pages, if
there are problems with migration this can flood the logs.  Printing all
the data hogs the CPU and cause some RT threads to run for a long time,
which may have some bad consequences.

Rate limit the page migration warnings in order to avoid this.

Link: https://lkml.kernel.org/r/20210505140542.24935-1-georgi.djakov@linaro.orgSigned-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -1406,6 +1406,8 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 	struct page *page, *head;
 	int ret = 0;
 	LIST_HEAD(source);
+	static DEFINE_RATELIMIT_STATE(migrate_rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
 
 	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
 		if (!pfn_valid(pfn))
@@ -1452,9 +1454,11 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 						    page_is_file_lru(page));
 
 		} else {
+			if (__ratelimit(&migrate_rs)) {
 				pr_warn("failed to isolate pfn %lx\n", pfn);
 				dump_page(page, "isolation failed");
 			}
+		}
 		put_page(page);
 	}
 	if (!list_empty(&source)) {
@@ -1482,10 +1486,12 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			(unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
 		if (ret) {
 			list_for_each_entry(page, &source, lru) {
-				pr_warn("migrating pfn %lx failed ret:%d ",
+				if (__ratelimit(&migrate_rs)) {
+					pr_warn("migrating pfn %lx failed ret:%d\n",
 						page_to_pfn(page), ret);
 					dump_page(page, "migration failure");
 				}
+			}
 			putback_movable_pages(&source);
 		}
 	}