raid5: enable log for raid array with cache disk

Now log is safe to enable for raid array with cache disk
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>

drivers/md/raid5.c

@@ -6329,8 +6329,11 @@ static void raid5_free_percpu(struct r5conf *conf)
 
 static void free_conf(struct r5conf *conf)
 {
+	if (conf->log)
+		r5l_exit_log(conf->log);
 	if (conf->shrinker.seeks)
 		unregister_shrinker(&conf->shrinker);
+
 	free_thread_groups(conf);
 	shrink_stripes(conf);
 	raid5_free_percpu(conf);
@@ -6996,6 +6999,14 @@ static int run(struct mddev *mddev)
 						mddev->queue);
 	}
 
+	if (journal_dev) {
+		char b[BDEVNAME_SIZE];
+
+		printk(KERN_INFO"md/raid:%s: using device %s as journal\n",
+		       mdname(mddev), bdevname(journal_dev->bdev, b));
+		r5l_init_log(conf, journal_dev);
+	}
+
 	return 0;
 abort:
 	md_unregister_thread(&mddev->thread);

include/uapi/linux/raid/md_p.h

@@ -322,6 +322,7 @@ struct mdp_superblock_1 {
 					|MD_FEATURE_NEW_OFFSET		\
 					|MD_FEATURE_RECOVERY_BITMAP	\
 					|MD_FEATURE_CLUSTERED		\
+					|MD_FEATURE_JOURNAL		\
 					)
 
 struct r5l_payload_header {