Re: [REGRESSION] 6.7.1: md: raid5 hang and unresponsive system; successfully bisected

[Dan Moulding <dan@danm.net>]

> Thanks a lot for the testing! Can you also give following patch a try?
> It removes the change to blk_plug, because Dan and Song are worried
> about performance degradation, so we need to verify the performance
> before consider that patch.
> 
> Anyway, I think following patch can fix this problem as well.
> 
> Thanks,
> Kuai
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 3ad5f3c7f91e..ae8665be9940 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -6728,6 +6728,9 @@ static void raid5d(struct md_thread *thread)
>                  int batch_size, released;
>                  unsigned int offset;
> 
> +               if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags))
> +                       goto skip;
> +
>                  released = release_stripe_list(conf, 
> conf->temp_inactive_list);
>                  if (released)
>                          clear_bit(R5_DID_ALLOC, &conf->cache_state);
> @@ -6766,6 +6769,7 @@ static void raid5d(struct md_thread *thread)
>                          spin_lock_irq(&conf->device_lock);
>                  }
>          }
> +skip:
>          pr_debug("%d stripes handled\n", handled);
> 
>          spin_unlock_irq(&conf->device_lock);

Yes, this patch also seems to work. I cannot reproduce the problem on
6.8-rc7 or 6.8.1 with just this one applied.

Cheers!

-- Dan