Re: 5.14.9 aarch64 OOPS Workqueue: btrfs-delalloc btrfs_work_helper

[Chris Murphy <lists@colorremedies.com>]

On Tue, Oct 26, 2021 at 3:14 AM Nikolay Borisov <nborisov@suse.com> wrote:

> I think I identified a race that could cause the crash, can you apply the
> following diff and re-run the tests and leave them for a couple of days.
> Preferably apply it on 5.4.10 so that there is the highest chance to reproduce:
>
> diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
> index 309516e6a968..a3d788dcbd34 100644
> --- a/fs/btrfs/async-thread.c
> +++ b/fs/btrfs/async-thread.c
> @@ -234,6 +234,11 @@ static void run_ordered_work(struct __btrfs_workqueue *wq,
>                                   ordered_list);
>                 if (!test_bit(WORK_DONE_BIT, &work->flags))
>                         break;
> +               /*
> +                * Orders all subsequent loads after WORK_DONE_BIT, paired with
> +                * the smp_mb__before_atomic in btrfs_work_helper
> +                */
> +               smp_rmb();
>
>                 /*
>                  * we are going to call the ordered done function, but
> @@ -317,6 +322,12 @@ static void btrfs_work_helper(struct work_struct *normal_work)
>         thresh_exec_hook(wq);
>         work->func(work);
>         if (need_order) {
> +               /*
> +                * Ensures all вритес done in ->func are ordered before
> +                * setting the WORK_DONE_BIT making them visible to ordered
> +                * func
> +                */
> +               smp_mb__before_atomic();
>                 set_bit(WORK_DONE_BIT, &work->flags);
>                 run_ordered_work(wq, work);
>         } else {
>

So far this appears to be working well - thanks!
https://bugzilla.redhat.com/show_bug.cgi?id=2011928#c54


--
Chris Murphy