Commit 6f56f0c4 authored by Yu Kuai's avatar Yu Kuai Committed by Song Liu
Browse files

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: default avatarYu Kuai <yukuai3@huawei.com>
Signed-off-by: default avatarSong Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230529132037.2124527-4-yukuai1@huaweicloud.com
parent 64e5e09a

drivers/md/md.c

+5 −0
Original line number Diff line number Diff line
@@ -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

drivers/md/md.h

+3 −0
Original line number Diff line number Diff line
@@ -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;