Re: [PATCH v16 5/8] media: core: Free range of buffers

[Hans Verkuil]

On 15/12/2023 10:08, Benjamin Gaignard wrote:
> Improve __vb2_queue_free() and __vb2_free_mem() to free
> range of buffers and not only the last few buffers.
> Intoduce starting index to be flexible on range and change the loops
> according to this parameters.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
>  .../media/common/videobuf2/videobuf2-core.c   | 62 +++++++++----------
>  1 file changed, 30 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 9509535a980c..67ce823a0196 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -525,17 +525,16 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>  }
>  
>  /*
> - * __vb2_free_mem() - release all video buffer memory for a given queue
> + * __vb2_free_mem() - release video buffer memory for a given range of
> + * buffers in a given queue
>   */
> -static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
> +static void __vb2_free_mem(struct vb2_queue *q, unsigned int start, unsigned int count)
>  {
> -	unsigned int buffer;
> +	unsigned int i;
>  	struct vb2_buffer *vb;
> -	unsigned int q_num_buffers = vb2_get_num_buffers(q);
>  
> -	for (buffer = q_num_buffers - buffers; buffer < q_num_buffers;
> -	     ++buffer) {
> -		vb = vb2_get_buffer(q, buffer);
> +	for (i = start; i < q->max_num_buffers && i < start + count; i++) {

I think the i < q->max_num_buffers check should be dropped. 'start + count'
should always be <= q->max_num_buffers. That's something that must be
checked in a higher level function.

> +		vb = vb2_get_buffer(q, i);
>  		if (!vb)
>  			continue;
>  
> @@ -550,35 +549,35 @@ static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
>  }
>  
>  /*
> - * __vb2_queue_free() - free buffers at the end of the queue - video memory and
> + * __vb2_queue_free() - free @count buffers from @start index of the queue - video memory and
>   * related information, if no buffers are left return the queue to an
>   * uninitialized state. Might be called even if the queue has already been freed.
>   */
> -static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
> +static void __vb2_queue_free(struct vb2_queue *q, unsigned int start, unsigned int count)
>  {
> -	unsigned int buffer;
> -	unsigned int q_num_buffers = vb2_get_num_buffers(q);
> +	unsigned int i;
>  
>  	lockdep_assert_held(&q->mmap_lock);
>  
>  	/* Call driver-provided cleanup function for each buffer, if provided */
> -	for (buffer = q_num_buffers - buffers; buffer < q_num_buffers;
> -	     ++buffer) {
> -		struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
> +	for (i = start; i < q->max_num_buffers && i < start + count; i++) {

Ditto, and also the various instances below.

> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
>  
> -		if (vb && vb->planes[0].mem_priv)
> +		if (!vb)
> +			continue;> +		if (vb->planes[0].mem_priv)

Why change this code?

>  			call_void_vb_qop(vb, buf_cleanup, vb);
>  	}
>  
>  	/* Release video buffer memory */
> -	__vb2_free_mem(q, buffers);
> +	__vb2_free_mem(q, start, count);
>  
>  #ifdef CONFIG_VIDEO_ADV_DEBUG
>  	/*
>  	 * Check that all the calls were balanced during the life-time of this
>  	 * queue. If not then dump the counters to the kernel log.
>  	 */
> -	if (q_num_buffers) {
> +	if (vb2_get_num_buffers(q)) {
>  		bool unbalanced = q->cnt_start_streaming != q->cnt_stop_streaming ||
>  				  q->cnt_prepare_streaming != q->cnt_unprepare_streaming ||
>  				  q->cnt_wait_prepare != q->cnt_wait_finish;
> @@ -604,8 +603,8 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>  		q->cnt_stop_streaming = 0;
>  		q->cnt_unprepare_streaming = 0;
>  	}
> -	for (buffer = 0; buffer < vb2_get_num_buffers(q); buffer++) {
> -		struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
> +	for (i = start; i < q->max_num_buffers && i < start + count; i++) {
> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
>  		bool unbalanced;
>  
>  		if (!vb)
> @@ -622,7 +621,7 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>  
>  		if (unbalanced) {
>  			pr_info("unbalanced counters for queue %p, buffer %d:\n",
> -				q, buffer);
> +				q, i);
>  			if (vb->cnt_buf_init != vb->cnt_buf_cleanup)
>  				pr_info("     buf_init: %u buf_cleanup: %u\n",
>  					vb->cnt_buf_init, vb->cnt_buf_cleanup);
> @@ -656,9 +655,8 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>  #endif
>  
>  	/* Free vb2 buffers */
> -	for (buffer = q_num_buffers - buffers; buffer < q_num_buffers;
> -	     ++buffer) {
> -		struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
> +	for (i = start; i < q->max_num_buffers && i < start + count; i++) {
> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
>  
>  		if (!vb)
>  			continue;
> @@ -698,7 +696,7 @@ EXPORT_SYMBOL(vb2_buffer_in_use);
>  static bool __buffers_in_use(struct vb2_queue *q)
>  {
>  	unsigned int buffer;
> -	for (buffer = 0; buffer < vb2_get_num_buffers(q); ++buffer) {
> +	for (buffer = 0; buffer < q->max_num_buffers; ++buffer) {
>  		struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>  
>  		if (!vb)
> @@ -858,7 +856,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  		 * queued without ever calling STREAMON.
>  		 */
>  		__vb2_queue_cancel(q);
> -		__vb2_queue_free(q, q_num_bufs);
> +		__vb2_queue_free(q, 0, q->max_num_buffers);
>  		mutex_unlock(&q->mmap_lock);
>  
>  		/*
> @@ -968,7 +966,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  		 * from already queued buffers and it will reset q->memory to
>  		 * VB2_MEMORY_UNKNOWN.
>  		 */
> -		__vb2_queue_free(q, allocated_buffers);
> +		__vb2_queue_free(q, first_index, allocated_buffers);
>  		mutex_unlock(&q->mmap_lock);
>  		return ret;
>  	}
> @@ -1008,7 +1006,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  	bool no_previous_buffers = !q_num_bufs;
>  	int ret = 0;
>  
> -	if (q->num_buffers == q->max_num_buffers) {
> +	if (q_num_bufs == q->max_num_buffers) {
>  		dprintk(q, 1, "maximum number of buffers already allocated\n");
>  		return -ENOBUFS;
>  	}
> @@ -1108,7 +1106,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  		 * from already queued buffers and it will reset q->memory to
>  		 * VB2_MEMORY_UNKNOWN.
>  		 */
> -		__vb2_queue_free(q, allocated_buffers);
> +		__vb2_queue_free(q, *first_index, allocated_buffers);
>  		mutex_unlock(&q->mmap_lock);
>  		return -ENOMEM;
>  	}
> @@ -1722,7 +1720,7 @@ static int vb2_start_streaming(struct vb2_queue *q)
>  		 * Forcefully reclaim buffers if the driver did not
>  		 * correctly return them to vb2.
>  		 */
> -		for (i = 0; i < vb2_get_num_buffers(q); ++i) {
> +		for (i = 0; i < q->max_num_buffers; ++i) {
>  			vb = vb2_get_buffer(q, i);
>  
>  			if (!vb)
> @@ -2128,7 +2126,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
>  	 * to vb2 in stop_streaming().
>  	 */
>  	if (WARN_ON(atomic_read(&q->owned_by_drv_count))) {
> -		for (i = 0; i < vb2_get_num_buffers(q); i++) {
> +		for (i = 0; i < q->max_num_buffers; i++) {
>  			struct vb2_buffer *vb = vb2_get_buffer(q, i);
>  
>  			if (!vb)
> @@ -2172,7 +2170,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
>  	 * call to __fill_user_buffer() after buf_finish(). That order can't
>  	 * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
>  	 */
> -	for (i = 0; i < vb2_get_num_buffers(q); i++) {
> +	for (i = 0; i < q->max_num_buffers; i++) {
>  		struct vb2_buffer *vb;
>  		struct media_request *req;
>  
> @@ -2586,7 +2584,7 @@ void vb2_core_queue_release(struct vb2_queue *q)
>  	__vb2_cleanup_fileio(q);
>  	__vb2_queue_cancel(q);
>  	mutex_lock(&q->mmap_lock);
> -	__vb2_queue_free(q, vb2_get_num_buffers(q));
> +	__vb2_queue_free(q, 0, q->max_num_buffers);
>  	kfree(q->bufs);
>  	q->bufs = NULL;
>  	bitmap_free(q->bufs_bitmap);

Regards,

	Hans