md: add a mutex to synchronize idle and frozen in action_store()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6OMCC
CVE: NA

--------------------------------

Currently, for idle and frozen, action_store will hold 'reconfig_mutex'
and call md_reap_sync_thread() to stop sync thread, however, this will
cause deadlock (explained in the next patch). In order to fix the
problem, following patch will release 'reconfig_mutex' and wait on
'resync_wait', like md_set_readonly() and do_md_stop() does.

Consider that action_store() will set/clear 'MD_RECOVERY_FROZEN'
unconditionally, which might cause unexpected problems, for example,
frozen just set 'MD_RECOVERY_FROZEN' and is still in progress, while
'idle' clear 'MD_RECOVERY_FROZEN' and new sync thread is started, which
might starve in progress frozen.

This patch add a mutex to synchronize idle and frozen from
action_store().
Signed-off-by: NYu Kuai <yukuai3@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>

drivers/md/md.c

@@ -690,6 +690,7 @@ void mddev_init(struct mddev *mddev)
 	mutex_init(&mddev->open_mutex);
 	mutex_init(&mddev->reconfig_mutex);
 	mutex_init(&mddev->bitmap_info.mutex);
+	mutex_init(&mddev->sync_mutex);
 	INIT_LIST_HEAD(&mddev->disks);
 	INIT_LIST_HEAD(&mddev->all_mddevs);
 	timer_setup(&mddev->safemode_timer, md_safemode_timeout, 0);
@@ -4885,14 +4886,18 @@ static void stop_sync_thread(struct mddev *mddev)
 
 static void idle_sync_thread(struct mddev *mddev)
 {
+	mutex_lock(&mddev->sync_mutex);
 	clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 	stop_sync_thread(mddev);
+	mutex_unlock(&mddev->sync_mutex);
 }
 
 static void frozen_sync_thread(struct mddev *mddev)
 {
+	mutex_lock(&mddev->sync_mutex);
 	set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 	stop_sync_thread(mddev);
+	mutex_unlock(&mddev->sync_mutex);
 }
 
 static ssize_t

drivers/md/md.h

@@ -528,6 +528,9 @@ struct mddev {
 	bool	has_superblocks:1;
 	bool	fail_last_dev:1;
 	bool	serialize_policy:1;
+
+	/* Used to synchronize idle and frozen for action_store() */
+	struct mutex sync_mutex;
 };
 
 enum recovery_flags {