[PATCH] mm/memory_hotplug: Rate limit page migration warnings

[Georgi Djakov <georgi.djakov@linaro.org>]

From: Liam Mark <lmark@codeaurora.org>

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.

Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
---
 mm/memory_hotplug.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 70620d0dd923..64acbdc6bece 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1521,6 +1521,8 @@ 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))
@@ -1567,8 +1569,10 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 						    page_is_file_lru(page));
 
 		} else {
-			pr_warn("failed to isolate pfn %lx\n", pfn);
-			dump_page(page, "isolation failed");
+			if (__ratelimit(&migrate_rs)) {
+				pr_warn("failed to isolate pfn %lx\n", pfn);
+				dump_page(page, "isolation failed");
+			}
 		}
 		put_page(page);
 	}
@@ -1597,9 +1601,11 @@ 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 ",
-				       page_to_pfn(page), ret);
-				dump_page(page, "migration failure");
+				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);
 		}