> diff --git i/drivers/md/md.c w/drivers/md/md.c
> index 6072782070230..49442a3f4605b 100644
> --- i/drivers/md/md.c
> +++ w/drivers/md/md.c
> @@ -7591,8 +7591,10 @@ static int md_ioctl(struct block_device *bdev,
> fmode_t mode,
>                         err = -EBUSY;
>                         goto out;
>                 }
> -               WARN_ON_ONCE(test_bit(MD_CLOSING, &mddev->flags));
> -               set_bit(MD_CLOSING, &mddev->flags);
> +               if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
> +                       err = -EBUSY;
> +                       goto out;
> +               }
>                 did_set_md_closing = true;
>                 mutex_unlock(&mddev->open_mutex);
>                 sync_blockdev(bdev);
> 
> Could you please test whether this fixes the issue?

Since &mddev->open_mutex is held when testing a bit of mddev->flags, I
modified the code just a little bit by putting mutex_unlock() as
belows.

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 98bac4f304ae..643f7f5be49b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7590,8 +7590,11 @@ static int md_ioctl(struct block_device *bdev, fmode_t 
mode,
                        err = -EBUSY;
                        goto out;
                }
-               WARN_ON_ONCE(test_bit(MD_CLOSING, &mddev->flags));
-               set_bit(MD_CLOSING, &mddev->flags);
+               if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
+                       mutex_unlock(&mddev->open_mutex);
+                       err = -EBUSY;
+                       goto out;
+               }
                did_set_md_closing = true;
                mutex_unlock(&mddev->open_mutex);
                sync_blockdev(bdev);

The warning no longer recurs (of course, we removed
WARN_ON_ONCE()). As I am not familiar with this code, I do not see any
other problem.

Best regards,
Dae R. Jeong


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