jbd2: Use pr_notice_ratelimited() in journal_alloc_journal_head()

We had an open-coded version of printk_ratelimited(); use the provided
abstraction to make the code cleaner and easier to understand.

Based on a similar patch for fs/jbd from Namhyung Kim <namhyung@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/jbd2/journal.c

@@ -43,6 +43,7 @@
 #include <linux/vmalloc.h>
 #include <linux/backing-dev.h>
 #include <linux/bitops.h>
+#include <linux/ratelimit.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/jbd2.h>
@@ -1982,7 +1983,6 @@ static void jbd2_journal_destroy_jbd2_journal_head_cache(void)
 static struct journal_head *journal_alloc_journal_head(void)
 {
 	struct journal_head *ret;
-	static unsigned long last_warning;
 
 #ifdef CONFIG_JBD2_DEBUG
 	atomic_inc(&nr_journal_heads);
@@ -1990,11 +1990,7 @@ static struct journal_head *journal_alloc_journal_head(void)
 	ret = kmem_cache_alloc(jbd2_journal_head_cache, GFP_NOFS);
 	if (!ret) {
 		jbd_debug(1, "out of memory for journal_head\n");
-		if (time_after(jiffies, last_warning + 5*HZ)) {
-			printk(KERN_NOTICE "ENOMEM in %s, retrying.\n",
-			       __func__);
-			last_warning = jiffies;
-		}
+		pr_notice_ratelimited("ENOMEM in %s, retrying.\n", __func__);
 		while (!ret) {
 			yield();
 			ret = kmem_cache_alloc(jbd2_journal_head_cache, GFP_NOFS);