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

Hans Verkuil
2023-09-19T15:00:45Z

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@collabora.com>
> ---
> .../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