md/r5cache: move mddev_lock() out of r5c_journal_mode_set()

r5c_journal_mode_set() is called by r5c_journal_mode_store() and
raid_ctr() in dm-raid. We don't need mddev_lock() when calling from
raid_ctr(). This patch fixes this by moves the mddev_lock() to
r5c_journal_mode_store().

Cc: stable@vger.kernel.org (v4.13+)
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

drivers/md/raid5-cache.c

@@ -2577,31 +2577,22 @@ static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
 int r5c_journal_mode_set(struct mddev *mddev, int mode)
 {
 	struct r5conf *conf;
-	int err;
 
 	if (mode < R5C_JOURNAL_MODE_WRITE_THROUGH ||
 	    mode > R5C_JOURNAL_MODE_WRITE_BACK)
 		return -EINVAL;
 
-	err = mddev_lock(mddev);
-	if (err)
-		return err;
 	conf = mddev->private;
-	if (!conf || !conf->log) {
-		mddev_unlock(mddev);
+	if (!conf || !conf->log)
 		return -ENODEV;
-	}
 
 	if (raid5_calc_degraded(conf) > 0 &&
-	    mode == R5C_JOURNAL_MODE_WRITE_BACK) {
-		mddev_unlock(mddev);
+	    mode == R5C_JOURNAL_MODE_WRITE_BACK)
 		return -EINVAL;
-	}
 
 	mddev_suspend(mddev);
 	conf->log->r5c_journal_mode = mode;
 	mddev_resume(mddev);
-	mddev_unlock(mddev);
 
 	pr_debug("md/raid:%s: setting r5c cache mode to %d: %s\n",
 		 mdname(mddev), mode, r5c_journal_mode_str[mode]);
@@ -2614,6 +2605,7 @@ static ssize_t r5c_journal_mode_store(struct mddev *mddev,
 {
 	int mode = ARRAY_SIZE(r5c_journal_mode_str);
 	size_t len = length;
+	int ret;
 
 	if (len < 2)
 		return -EINVAL;
@@ -2625,8 +2617,12 @@ static ssize_t r5c_journal_mode_store(struct mddev *mddev,
 		if (strlen(r5c_journal_mode_str[mode]) == len &&
 		    !strncmp(page, r5c_journal_mode_str[mode], len))
 			break;
-
-	return r5c_journal_mode_set(mddev, mode) ?: length;
+	ret = mddev_lock(mddev);
+	if (ret)
+		return ret;
+	ret = r5c_journal_mode_set(mddev, mode);
+	mddev_unlock(mddev);
+	return ret ?: length;
 }
 
 struct md_sysfs_entry