md/r5cache: call mddev_lock/unlock() in r5c_journal_mode_set

In r5c_journal_mode_set(), it is necessary to call mddev_lock()
before accessing conf and conf->log. Otherwise, the conf->log
may change (and become NULL).

Shaohua: fix unlock in failure cases

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index bfa1e907c472e49855f9e0abb4c307cd45514d4d..ce98414a6e34e62d049dd84b34fb1b74fcb02003 100644 (file)
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -2540,23 +2540,32 @@ 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 = mddev->private;
-       struct r5l_log *log = conf->log;
-
-       if (!log)
-               return -ENODEV;
+       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);
+               return -ENODEV;
+       }
+
        if (raid5_calc_degraded(conf) > 0 &&
-           mode == R5C_JOURNAL_MODE_WRITE_BACK)
+           mode == R5C_JOURNAL_MODE_WRITE_BACK) {
+               mddev_unlock(mddev);
                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]);