linux-kernel - Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on eviction error

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Date:   Thu, 22 Jun 2023 15:55:22 +0200
From:   Andi Shyti <andi.shyti@...ux.intel.com>
To:     Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>
Cc:     intel-xe@...ts.freedesktop.org,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Christian König 
        <ckoenig.leichtzumerken@...il.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Huang Rui <ray.huang@....com>,
        dri-devel@...ts.freedesktop.org,
        Christian König <christian.koenig@....com>
Subject: Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on
 eviction error

Hi Thomas,

On Thu, Jun 22, 2023 at 12:14:11PM +0200, Thomas Hellström wrote:
> On eviction errors other than -EMULTIHOP we were leaking a resource.
> Fix.
> 
> Fixes: 403797925768 ("drm/ttm: Fix multihop assert on eviction.")
> Cc: Andrey Grodzovsky <andrey.grodzovsky@....com>
> Cc: Christian König <christian.koenig@....com>
> Cc: Christian Koenig <christian.koenig@....com>
> Cc: Huang Rui <ray.huang@....com>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: <stable@...r.kernel.org> # v5.15+
> Signed-off-by: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 615d30c4262d..89530f2a027f 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -462,14 +462,14 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
>  	ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
>  	if (ret == -EMULTIHOP) {
>  		ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem, ctx, &hop);
> -		if (ret) {
> -			if (ret != -ERESTARTSYS && ret != -EINTR)
> -				pr_err("Buffer eviction failed\n");
> -			ttm_resource_free(bo, &evict_mem);
> -			goto out;
> -		}
> -		/* try and move to final place now. */
> -		goto bounce;
> +		if (!ret)
> +			/* try and move to final place now. */
> +			goto bounce;

As we are at this, can't we replace this with a while()? Goto's
used instead of a while loop are a fist in the eye...

It looks even better:

	while (1) {
		ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
		if (!ret)
			break;

		if (ret == -EMULTIHOP)
			ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem,
							ctx, &hop);

		/* try again */
		if (!ret)
			continue;

		ttm_resource_free(bo, &evict_mem);
		if (ret != -ERESTARTSYS && ret != -EINTR)
			pr_err("Buffer eviction failed\n");

		break;
	}

Andi

> +	}
> +	if (ret) {
> +		ttm_resource_free(bo, &evict_mem);
> +		if (ret != -ERESTARTSYS && ret != -EINTR)
> +			pr_err("Buffer eviction failed\n");
>  	}
>  out:
>  	return ret;
> -- 
> 2.40.1