Re: [PATCH v7 45/49] media: core: Add bitmap manage bufs array entries

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On 14/09/2023 15:33, Benjamin Gaignard wrote:
> Add a bitmap field to know which of bufs array entries are
> used or not.
> Remove no more used num_buffers field from queue structure.
> Use bitmap_find_next_zero_area() to find the first possible
> range when creating new buffers to fill the gaps.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
>  .../media/common/videobuf2/videobuf2-core.c   | 55 +++++++++++++++----
>  include/media/videobuf2-core.h                |  9 ++-
>  2 files changed, 51 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index a4c2fae8705d..c5d4a388331b 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -411,10 +411,11 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
>   */
>  static bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
>  {
> -	if (index < q->max_allowed_buffers && !q->bufs[index]) {
> +	if (index < q->max_allowed_buffers && !test_bit(index, q->bufs_map)) {

I think bufs_bitmap would be a better name.

>  		q->bufs[index] = vb;
>  		vb->index = index;
>  		vb->vb2_queue = q;
> +		set_bit(index, q->bufs_map);
>  		return true;
>  	}
>  
> @@ -428,9 +429,10 @@ static bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, uns
>   */
>  static void vb2_queue_remove_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>  {
> -	if (vb->index < q->max_allowed_buffers) {
> +	if (vb->index < q->max_allowed_buffers && test_bit(vb->index, q->bufs_map)) {

As mentioned in past reviews, I think these tests can be dropped, it makes no
sense that these ever fail.

>  		q->bufs[vb->index] = NULL;
>  		vb->vb2_queue = NULL;
> +		clear_bit(vb->index, q->bufs_map);
>  	}
>  }
>  
> @@ -451,11 +453,12 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>  	unsigned long first_index;
>  	int ret;
>  
> -	/* Ensure that q->num_buffers+num_buffers is below q->max_allowed_buffers */
> +	/* Ensure that the number of already queue + num_buffers is below q->max_allowed_buffers */

Hmm, how about:

	/* Ensure that vb2_get_num_buffers(q) + num_buffers is no more than q->max_allowed_buffers */

>  	num_buffers = min_t(unsigned int, num_buffers,
>  			    q->max_allowed_buffers - vb2_get_num_buffers(q));
>  
> -	first_index = vb2_get_num_buffers(q);
> +	first_index = bitmap_find_next_zero_area(q->bufs_map, q->max_allowed_buffers,
> +						 0, num_buffers, 0);
>  
>  	if (first_index >= q->max_allowed_buffers)
>  		return 0;
> @@ -675,7 +678,13 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>  
>  struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q, unsigned int index)
>  {
> -	if (index < q->num_buffers)
> +	if (!q->bufs_map || !q->bufs)
> +		return NULL;

I don't think this can ever happen.

> +
> +	if (index >= q->max_allowed_buffers)
> +		return NULL;
> +
> +	if (test_bit(index, q->bufs_map))
>  		return q->bufs[index];
>  	return NULL;
>  }
> @@ -683,7 +692,10 @@ EXPORT_SYMBOL_GPL(vb2_get_buffer);
>  
>  unsigned int vb2_get_num_buffers(struct vb2_queue *q)
>  {
> -	return q->num_buffers;
> +	if (!q->bufs_map)
> +		return 0;

Ditto.

> +
> +	return bitmap_weight(q->bufs_map, q->max_allowed_buffers);
>  }
>  EXPORT_SYMBOL_GPL(vb2_get_num_buffers);
>  
> @@ -899,6 +911,14 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  		q->bufs = kcalloc(q->max_allowed_buffers, sizeof(*q->bufs), GFP_KERNEL);
>  	if (!q->bufs)
>  		ret = -ENOMEM;
> +
> +	if (!q->bufs_map)
> +		q->bufs_map = bitmap_zalloc(q->max_allowed_buffers, GFP_KERNEL);
> +	if (!q->bufs_map) {
> +		ret = -ENOMEM;
> +		kfree(q->bufs);
> +		q->bufs = NULL;
> +	}
>  	q->memory = memory;
>  	mutex_unlock(&q->mmap_lock);
>  	if (ret)
> @@ -968,7 +988,6 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  	}
>  
>  	mutex_lock(&q->mmap_lock);
> -	q->num_buffers = allocated_buffers;
>  
>  	if (ret < 0) {
>  		/*
> @@ -995,6 +1014,10 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  	mutex_lock(&q->mmap_lock);
>  	q->memory = VB2_MEMORY_UNKNOWN;
>  	mutex_unlock(&q->mmap_lock);
> +	kfree(q->bufs);
> +	q->bufs = NULL;
> +	bitmap_free(q->bufs_map);
> +	q->bufs_map = NULL;
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
> @@ -1031,9 +1054,19 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  		q->memory = memory;
>  		if (!q->bufs)
>  			q->bufs = kcalloc(q->max_allowed_buffers, sizeof(*q->bufs), GFP_KERNEL);
> -		if (!q->bufs)
> +		if (!q->bufs) {
> +			ret = -ENOMEM;
> +			goto unlock;
> +		}
> +		if (!q->bufs_map)
> +			q->bufs_map = bitmap_zalloc(q->max_allowed_buffers, GFP_KERNEL);
> +		if (!q->bufs_map) {
>  			ret = -ENOMEM;
> +			kfree(q->bufs);
> +			q->bufs = NULL;
> +		}
>  		mutex_unlock(&q->mmap_lock);
> +unlock:
>  		if (ret)
>  			return ret;
>  		q->waiting_for_buffers = !q->is_output;
> @@ -1095,7 +1128,6 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  	}
>  
>  	mutex_lock(&q->mmap_lock);
> -	q->num_buffers += allocated_buffers;
>  
>  	if (ret < 0) {
>  		/*
> @@ -2588,6 +2620,9 @@ void vb2_core_queue_release(struct vb2_queue *q)
>  	__vb2_queue_free(q, q->max_allowed_buffers);
>  	kfree(q->bufs);
>  	q->bufs = NULL;
> +	bitmap_free(q->bufs_map);
> +	q->bufs_map = NULL;
> +
>  	mutex_unlock(&q->mmap_lock);
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_queue_release);
> @@ -2944,7 +2979,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>  	 * Check if we need to dequeue the buffer.
>  	 */
>  	index = fileio->cur_index;
> -	if (index >= q->num_buffers) {
> +	if (!test_bit(index, q->bufs_map)) {
>  		struct vb2_buffer *b;
>  
>  		/*
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 19c93d8eb7c8..734437236cc4 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -557,7 +557,7 @@ struct vb2_buf_ops {
>   * @memory:	current memory type used
>   * @dma_dir:	DMA mapping direction.
>   * @bufs:	videobuf2 buffer structures
> - * @num_buffers: number of allocated/used buffers
> + * @bufs_map:	bitmap to manage bufs entries.
>   * @max_allowed_buffers: upper limit of number of allocated/used buffers
>   * @queued_list: list of buffers currently queued from userspace
>   * @queued_count: number of buffers queued and ready for streaming.
> @@ -621,7 +621,7 @@ struct vb2_queue {
>  	unsigned int			memory;
>  	enum dma_data_direction		dma_dir;
>  	struct vb2_buffer		**bufs;
> -	unsigned int			num_buffers;
> +	unsigned long			*bufs_map;
>  	unsigned int			max_allowed_buffers;
>  
>  	struct list_head		queued_list;
> @@ -1151,7 +1151,10 @@ static inline bool vb2_fileio_is_active(struct vb2_queue *q)
>   */
>  static inline bool vb2_is_busy(struct vb2_queue *q)
>  {
> -	return (q->num_buffers > 0);
> +	if (!q->bufs_map)
> +		return false;

I don't think this can happen.

> +
> +	return (bitmap_weight(q->bufs_map, q->max_allowed_buffers) > 0);

How about:

	return vb2_get_num_buffers(q) > 0;

>  }
>  
>  /**

Regards,

	Hans



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