Re: [PATCH v2 3/8] mm: Optimise madvise WILLNEED

[Qian Cai <cai-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Mon, 2020-09-14 at 17:50 +0100, Matthew Wilcox wrote:
> On Mon, Sep 14, 2020 at 12:17:07PM -0400, Qian Cai wrote:
> > Reverting the "Return head pages from find_*_entry" patchset [1] up to this
> > patch fixed the issue that LTP madvise06 test [2] would trigger endless
> > soft-
> > lockups below. It does not help after applied patches fixed other separate
> > issues in the patchset [3][4].
> 
> Thanks for the report.  Could you try this?

It works fine.

> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 96189acd6969..2d9ceccb338d 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -234,6 +234,7 @@ static void force_shm_swapin_readahead(struct
> vm_area_struct *vma,
>  
>  		if (!xa_is_value(page))
>  			continue;
> +		xas_pause(&xas);
>  		rcu_read_unlock();
>  
>  		swap = radix_to_swp_entry(page);
> @@ -243,7 +244,6 @@ static void force_shm_swapin_readahead(struct
> vm_area_struct *vma,
>  			put_page(page);
>  
>  		rcu_read_lock();
> -		xas_reset(&xas);
>  	}
>  	rcu_read_unlock();
>  
>