On 4/13/21 9:07 AM, Sudhakar Panneerselvam wrote:

NULL pointer dereference was observed in super_written() when it tries
to access the mddev structure.

[The below stack trace is from an older kernel, but the problem described
in this patch applies to the mainline kernel.]
... ...

The solution is to call md_super_wait() for external bitmaps after the
last call to md_bitmap_daemon_work() in md_bitmap_flush() to ensure there
are no pending bitmap writes before proceeding with the tear down.

Signed-off-by: Sudhakar Panneerselvam <redacted>
Reviewed-by: Heming Zhao <redacted>
---
  drivers/md/md-bitmap.c | 2 ++
  1 file changed, 2 insertions(+)

Hello Sudhakar,

A few info to you. If I understand kernel patch submit rules correctly.
1.
You couldn't add the line "Reviewed-by: Heming Zhao [off-list ref]" before
I give you this line in my email.
But take it easy, you can add my name now.

2.
This is v2 patch, you should change title from [PATCH] to [PATCH v2], and
also need to write changelog in patch.

Thanks,
Heming