From 6f56f0c4f1241f1694a6a9438dd4f78d4513a917 Mon Sep 17 00:00:00 2001
From: Yu Kuai <yukuai3@huawei.com>
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 <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
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 7fa91f0e56202..3d7e87cab8ad6 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 1aef86bf3fc31..18c168bf5fabe 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;
--
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