Re: [PATCH v3] drm/i915: Handle incomplete Z_FINISH for compressed error states

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 03/10/2018 09:24, Chris Wilson wrote:
> The final call to zlib_deflate(Z_FINISH) may require more output
> space to be allocated and so needs to re-invoked. Failure to do so in
> the current code leads to incomplete zlib streams (albeit intact due to
> the use of Z_SYNC_FLUSH) resulting in the occasional short object
> capture.
> 
> v2: Check against overrunning our pre-allocated page array
> v3: Drop Z_SYNC_FLUSH entirely
> 
> Testcase: igt/i915-error-capture.js
> Fixes: 0a97015d45ee ("drm/i915: Compress GPU objects in error state")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: <stable@vger.kernel.org> # v4.10+
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gpu_error.c | 88 +++++++++++++++++++--------
>   drivers/gpu/drm/i915/i915_gpu_error.h |  1 +
>   2 files changed, 64 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> index 3d5554f14dfd..705ff122100f 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -232,6 +232,20 @@ static bool compress_init(struct compress *c)
>   	return true;
>   }
>   
> +static void *compress_next_page(struct drm_i915_error_object *dst)
> +{
> +	unsigned long page;
> +
> +	if (dst->page_count >= dst->num_pages)
> +		return ERR_PTR(-ENOSPC);
> +
> +	page = __get_free_page(GFP_ATOMIC | __GFP_NOWARN);
> +	if (!page)
> +		return ERR_PTR(-ENOMEM);
> +
> +	return dst->pages[dst->page_count++] = (void *)page;
> +}
> +
>   static int compress_page(struct compress *c,
>   			 void *src,
>   			 struct drm_i915_error_object *dst)
> @@ -245,19 +259,14 @@ static int compress_page(struct compress *c,
>   
>   	do {
>   		if (zstream->avail_out == 0) {
> -			unsigned long page;
> -
> -			page = __get_free_page(GFP_ATOMIC | __GFP_NOWARN);
> -			if (!page)
> -				return -ENOMEM;
> +			zstream->next_out = compress_next_page(dst);
> +			if (IS_ERR(zstream->next_out))
> +				return PTR_ERR(zstream->next_out);
>   
> -			dst->pages[dst->page_count++] = (void *)page;
> -
> -			zstream->next_out = (void *)page;
>   			zstream->avail_out = PAGE_SIZE;
>   		}
>   
> -		if (zlib_deflate(zstream, Z_SYNC_FLUSH) != Z_OK)
> +		if (zlib_deflate(zstream, Z_NO_FLUSH) != Z_OK)
>   			return -EIO;
>   	} while (zstream->avail_in);
>   
> @@ -268,19 +277,42 @@ static int compress_page(struct compress *c,
>   	return 0;
>   }
>   
> -static void compress_fini(struct compress *c,
> +static int compress_flush(struct compress *c,
>   			  struct drm_i915_error_object *dst)
>   {
>   	struct z_stream_s *zstream = &c->zstream;
>   
> -	if (dst) {
> -		zlib_deflate(zstream, Z_FINISH);
> -		dst->unused = zstream->avail_out;
> -	}
> +	do {
> +		switch (zlib_deflate(zstream, Z_FINISH)) {
> +		case Z_OK: /* more space requested */
> +			zstream->next_out = compress_next_page(dst);
> +			if (IS_ERR(zstream->next_out))
> +				return PTR_ERR(zstream->next_out);
> +
> +			zstream->avail_out = PAGE_SIZE;
> +			break;
> +
> +		case Z_STREAM_END:
> +			goto end;
> +
> +		default: /* any error */
> +			return -EIO;
> +		}
> +	} while (1);
> +
> +end:
> +	memset(zstream->next_out, 0, zstream->avail_out);
> +	dst->unused = zstream->avail_out;
> +	return 0;
> +}
> +
> +static void compress_fini(struct compress *c,
> +			  struct drm_i915_error_object *dst)
> +{
> +	struct z_stream_s *zstream = &c->zstream;
>   
>   	zlib_deflateEnd(zstream);
>   	kfree(zstream->workspace);
> -
>   	if (c->tmp)
>   		free_page((unsigned long)c->tmp);
>   }
> @@ -319,6 +351,12 @@ static int compress_page(struct compress *c,
>   	return 0;
>   }
>   
> +static int compress_flush(struct compress *c,
> +			  struct drm_i915_error_object *dst)
> +{
> +	return 0;
> +}
> +
>   static void compress_fini(struct compress *c,
>   			  struct drm_i915_error_object *dst)
>   {
> @@ -917,6 +955,7 @@ i915_error_object_create(struct drm_i915_private *i915,
>   	unsigned long num_pages;
>   	struct sgt_iter iter;
>   	dma_addr_t dma;
> +	int ret;
>   
>   	if (!vma)
>   		return NULL;
> @@ -930,6 +969,7 @@ i915_error_object_create(struct drm_i915_private *i915,
>   
>   	dst->gtt_offset = vma->node.start;
>   	dst->gtt_size = vma->node.size;
> +	dst->num_pages = num_pages;
>   	dst->page_count = 0;
>   	dst->unused = 0;
>   
> @@ -938,28 +978,26 @@ i915_error_object_create(struct drm_i915_private *i915,
>   		return NULL;
>   	}
>   
> +	ret = -EINVAL;
>   	for_each_sgt_dma(dma, iter, vma->pages)  >   		void __iomem *s;
> -		int ret;
>   
>   		ggtt->vm.insert_page(&ggtt->vm, dma, slot, I915_CACHE_NONE, 0);
>   
>   		s = io_mapping_map_atomic_wc(&ggtt->iomap, slot);
>   		ret = compress_page(&compress, (void  __force *)s, dst);
>   		io_mapping_unmap_atomic(s);
> -
>   		if (ret)
> -			goto unwind;
> +			break;
>   	}
> -	goto out;
>   
> -unwind:
> -	while (dst->page_count--)
> -		free_page((unsigned long)dst->pages[dst->page_count]);
> -	kfree(dst);
> -	dst = NULL;
> +	if (ret || compress_flush(&compress, dst)) {
> +		while (dst->page_count--)
> +			free_page((unsigned long)dst->pages[dst->page_count]);
> +		kfree(dst);
> +		dst = NULL;
> +	}
>   
> -out:
>   	compress_fini(&compress, dst);
>   	ggtt->vm.clear_range(&ggtt->vm, slot, PAGE_SIZE);
>   	return dst;
> diff --git a/drivers/gpu/drm/i915/i915_gpu_error.h b/drivers/gpu/drm/i915/i915_gpu_error.h
> index f893a4e8b783..8710fb18ed74 100644
> --- a/drivers/gpu/drm/i915/i915_gpu_error.h
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.h
> @@ -135,6 +135,7 @@ struct i915_gpu_state {
>   		struct drm_i915_error_object {
>   			u64 gtt_offset;
>   			u64 gtt_size;
> +			int num_pages;
>   			int page_count;
>   			int unused;
>   			u32 *pages[0];
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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