From: Yu Kuai <redacted>

stop_sync_thread(), md_set_readonly() and do_md_stop() are trying to
stop sync_thread() the same way, hence factor out a helper to make code
cleaner, and also prepare to use the new helper to fix problems later.

Signed-off-by: Yu Kuai <redacted>
Signed-off-by: Yu Kuai <redacted>
---
 drivers/md/md.c | 129 ++++++++++++++++++++++++++----------------------
 1 file changed, 69 insertions(+), 60 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c0f2bdafe46a..7252fae0c989 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c

@@ -4848,29 +4848,46 @@ action_show(struct mddev *mddev, char *page)
        return sprintf(page, "%s\n", type);
 }

-static int stop_sync_thread(struct mddev *mddev)
+static bool sync_thread_stopped(struct mddev *mddev, int *seq_ptr)
 {
-       int ret = 0;
+       if (seq_ptr && *seq_ptr != atomic_read(&mddev->sync_seq))
+               return true;

-       if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
-               return 0;
+       return (!mddev->sync_thread &&
+               !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+}

-       ret = mddev_lock(mddev);
-       if (ret)
-               return ret;
+/*
+ * stop_sync_thread() - stop running sync_thread.
+ * @mddev: the array that sync_thread belongs to.
+ * @freeze: set true to prevent new sync_thread to start.
+ * @interruptible: if set true, then user can interrupt while waiting for
+ * sync_thread to be done.
+ *
+ * Noted that this function must be called with 'reconfig_mutex' grabbed, and
+ * fter this function return, 'reconfig_mtuex' will be released.
+ */
+static int stop_sync_thread(struct mddev *mddev, bool freeze,
+                           bool interruptible)
+       __releases(&mddev->reconfig_mutex)
+{
+       int *seq_ptr = NULL;
+       int sync_seq;
+       int ret = 0;
+
+       if (freeze) {
+               set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+       } else {
+               clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+               sync_seq = atomic_read(&mddev->sync_seq);
+               seq_ptr = &sync_seq;
+       }

-       /*
-        * Check again in case MD_RECOVERY_RUNNING is cleared before lock is
-        * held.
-        */
        if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
                mddev_unlock(mddev);
                return 0;
        }

-       if (work_pending(&mddev->sync_work))
-               flush_workqueue(md_misc_wq);
-
        set_bit(MD_RECOVERY_INTR, &mddev->recovery);
        /*
         * Thread might be blocked waiting for metadata update which will now

@@ -4879,53 +4896,58 @@ static int stop_sync_thread(struct mddev *mddev)
        md_wakeup_thread_directly(mddev->sync_thread);

        mddev_unlock(mddev);
-       return 0;
+       if (work_pending(&mddev->sync_work))
+               flush_work(&mddev->sync_work);
+
+       if (interruptible)
+               ret = wait_event_interruptible(resync_wait,
+                                       sync_thread_stopped(mddev, seq_ptr));
+       else
+               wait_event(resync_wait, sync_thread_stopped(mddev, seq_ptr));
+
+       return ret;
 }

 static int idle_sync_thread(struct mddev *mddev)
 {
        int ret;
-       int sync_seq = atomic_read(&mddev->sync_seq);
        bool flag;

        ret = mutex_lock_interruptible(&mddev->sync_mutex);
        if (ret)
                return ret;

-       flag = test_and_clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-       ret = stop_sync_thread(mddev);
+       flag = test_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+       ret = mddev_lock(mddev);
        if (ret)
-               goto out;
+               goto unlock;

-       ret = wait_event_interruptible(resync_wait,
-                       sync_seq != atomic_read(&mddev->sync_seq) ||
-                       !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
-out:
+       ret = stop_sync_thread(mddev, false, true);
        if (ret && flag)
                set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+unlock:
        mutex_unlock(&mddev->sync_mutex);
        return ret;
 }

 static int frozen_sync_thread(struct mddev *mddev)
 {
-       int ret = mutex_lock_interruptible(&mddev->sync_mutex);
+       int ret;
        bool flag;

+       ret = mutex_lock_interruptible(&mddev->sync_mutex);
        if (ret)
                return ret;

-       flag = test_and_set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-       ret = stop_sync_thread(mddev);
+       flag = test_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+       ret = mddev_lock(mddev);
        if (ret)
-               goto out;
+               goto unlock;

-       ret = wait_event_interruptible(resync_wait,
-                       mddev->sync_thread == NULL &&
-                       !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
-out:
+       ret = stop_sync_thread(mddev, true, true);
        if (ret && !flag)
                clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+unlock:
        mutex_unlock(&mddev->sync_mutex);
        return ret;
 }

@@ -6397,22 +6419,10 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
        if (mddev->external && test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags))
                return -EBUSY;

-       if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {
+       if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
                did_freeze = 1;
-               set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
-       }
-       if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
-               set_bit(MD_RECOVERY_INTR, &mddev->recovery);

-       /*
-        * Thread might be blocked waiting for metadata update which will now
-        * never happen
-        */
-       md_wakeup_thread_directly(mddev->sync_thread);
-
-       mddev_unlock(mddev);
-       wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
-                                         &mddev->recovery));
+       stop_sync_thread(mddev, true, false);
        wait_event(mddev->sb_wait,
                   !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
        mddev_lock_nointr(mddev);

@@ -6421,6 +6431,10 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
        if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) ||
            mddev->sync_thread ||
            test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+               /*
+                * This could happen if user change array state through
+                * ioctl/sysfs while reconfig_mutex is released.
+                */
                pr_warn("md: %s still in use.\n",mdname(mddev));
                err = -EBUSY;
                goto out;

@@ -6457,30 +6471,25 @@ static int do_md_stop(struct mddev *mddev, int mode,
        struct md_rdev *rdev;
        int did_freeze = 0;

-       if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)) {
+       if (!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
                did_freeze = 1;
+
+       if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+               stop_sync_thread(mddev, true, false);
+               mddev_lock_nointr(mddev);
+       } else {
                set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
        }
-       if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
-               set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-
-       /*
-        * Thread might be blocked waiting for metadata update which will now
-        * never happen
-        */
-       md_wakeup_thread_directly(mddev->sync_thread);
-
-       mddev_unlock(mddev);
-       wait_event(resync_wait, (mddev->sync_thread == NULL &&
-                                !test_bit(MD_RECOVERY_RUNNING,
-                                          &mddev->recovery)));
-       mddev_lock_nointr(mddev);

        mutex_lock(&mddev->open_mutex);
        if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) ||
            mddev->sysfs_active ||
            mddev->sync_thread ||
            test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+               /*
+                * This could happen if user change array state through
+                * ioctl/sysfs while reconfig_mutex is released.
+                */
                pr_warn("md: %s still in use.\n",mdname(mddev));
                mutex_unlock(&mddev->open_mutex);
                if (did_freeze) {
--

2.39.2