From 6f56f0c4f1241f1694a6a9438dd4f78d4513a917 Mon Sep 17 00:00:00 2001 From: Yu Kuai Date: Mon, 29 May 2023 21:20:34 +0800 Subject: [PATCH] md: add a mutex to synchronize idle and frozen in action_store() 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. A mutex is added to synchronize idle and frozen from action_store(). Signed-off-by: Yu Kuai Signed-off-by: Song Liu Link: https://lore.kernel.org/r/20230529132037.2124527-4-yukuai1@huaweicloud.com --- drivers/md/md.c | 5 +++++ drivers/md/md.h | 3 +++ 2 files changed, 8 insertions(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index 7fa91f0..3d7e87c 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -643,6 +643,7 @@ void mddev_init(struct mddev *mddev) { mutex_init(&mddev->open_mutex); mutex_init(&mddev->reconfig_mutex); + mutex_init(&mddev->sync_mutex); mutex_init(&mddev->bitmap_info.mutex); INIT_LIST_HEAD(&mddev->disks); INIT_LIST_HEAD(&mddev->all_mddevs); @@ -4777,14 +4778,18 @@ 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 diff --git a/drivers/md/md.h b/drivers/md/md.h index 1aef86b..18c168bf 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -535,6 +535,9 @@ struct mddev { */ struct list_head deleting; + /* Used to synchronize idle and frozen for action_store() */ + struct mutex sync_mutex; + bool has_superblocks:1; bool fail_last_dev:1; bool serialize_policy:1; -- 2.7.4