quoted

In my opinion, using a special wait is more clear than calling general md_bitmap_wait_writes(). the md_bitmap_wait_writes makes people

feel bitmap module does repetitive clean job.

quoted

My idea like:

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 200c5d0f08bf..ea6fa5a2cb6b 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -1723,6 +1723,8 @@ void md_bitmap_flush(struct mddev *mddev)
         bitmap->daemon_lastrun -= sleep;
         md_bitmap_daemon_work(mddev);
         md_bitmap_update_sb(bitmap);
+       if (mddev->bitmap_info.external)
+               md_super_wait(mddev);

Agreed. This looks much cleaner.

quoted

  }

  /*

@@ -1746,6 +1748,7 @@ void md_bitmap_free(struct bitmap *bitmap)
         /* Shouldn't be needed - but just in case.... */
         wait_event(bitmap->write_wait,
                    atomic_read(&bitmap->pending_writes) == 0);
+       wait_event(mddev->sb_wait, atomic_read(&mddev->pending_writes)==0);

I think this call looks redundant as this wait is already covered by md_update_sb() for non-external bitmaps and the proposed change in md_bitmap_flush() for external bitmaps. So, can we omit this change? 

quoted

         /* release the bitmap file  */
         md_bitmap_file_unmap(&bitmap->storage);

I like Heming's version better.

Hi Sudhakar,

Are you able to reproduce the issue? If so, could you please verify
that Heming's
change fixes the issue?

Hi Song, Heming,

Please review my comments above. I can try to reproduce the issue with the fix once we agree on the final fix.

Thanks
Sudhakar

Thanks,
Song