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

Benjamin Gaignard
2023-09-20T14:31:02Z

Le 19/09/2023 à 17:00, Hans Verkuil a écrit :
> 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.

Ok I will change it

>
>> 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.

I will drop them.

>
>> 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 */

sure

>
>> 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.

I got kernel crash without them.
I will keep them.

>
>> +
>> + 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;

vb2_get_num_buffers is defined in videobuf2-core.c, I'm not sure that
an inline function could depend of a module function.

Regards,
Benjamin

>
>> }
>>
>> /**
> Regards,
>
> Hans
>