[PATCH] drm/ttm: stop warning on TT shrinker failure

[Daniel Vetter]

On Fri, Mar 19, 2021 at 03:08:57PM +0100, Christian König wrote:
> Don't print a warning when we fail to allocate a page for swapping things out.
> 
> Also rely on memalloc_nofs_save/memalloc_nofs_restore instead of GFP_NOFS.

Uh this part doesn't make sense. Especially since you only do it for the
debugfs file, not in general. Which means you've just completely broken
the shrinker.

If this is just to paper over the seq_printf doing the wrong allocations,
then just move that out from under the fs_reclaim_acquire/release part.

__GFP_NOWARN should be there indeed I think.
-Daniel

> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/gpu/drm/ttm/ttm_tt.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> index 2f0833c98d2c..86fa3e82dacc 100644
> --- a/drivers/gpu/drm/ttm/ttm_tt.c
> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
> @@ -369,7 +369,7 @@ static unsigned long ttm_tt_shrinker_scan(struct shrinker *shrink,
>  	};
>  	int ret;
>  
> -	ret = ttm_bo_swapout(&ctx, GFP_NOFS);
> +	ret = ttm_bo_swapout(&ctx, GFP_KERNEL | __GFP_NOWARN);
>  	return ret < 0 ? SHRINK_EMPTY : ret;
>  }
>  
> @@ -389,10 +389,13 @@ static unsigned long ttm_tt_shrinker_count(struct shrinker *shrink,
>  static int ttm_tt_debugfs_shrink_show(struct seq_file *m, void *data)
>  {
>  	struct shrink_control sc = { .gfp_mask = GFP_KERNEL };
> +	unsigned int flags;
>  
>  	fs_reclaim_acquire(GFP_KERNEL);
> +	flags = memalloc_nofs_save();
>  	seq_printf(m, "%lu/%lu\n", ttm_tt_shrinker_count(&mm_shrinker, &sc),
>  		   ttm_tt_shrinker_scan(&mm_shrinker, &sc));
> +	memalloc_nofs_restore(flags);
>  	fs_reclaim_release(GFP_KERNEL);
>  
>  	return 0;
> -- 
> 2.25.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch