[v14,43/56] media: videobuf2: Be more flexible on the number of queue stored buffers

Message ID 20231031163104.112469-44-benjamin.gaignard@collabora.com
State New
Headers
Series Add DELETE_BUF ioctl |

Commit Message

Benjamin Gaignard Oct. 31, 2023, 4:30 p.m. UTC
  Add 'max_num_buffers' field in vb2_queue struct to let drivers decide
how many buffers could be stored in a queue.
This require 'bufs' array to be allocated at queue init time and freed
when releasing the queue.
By default VB2_MAX_FRAME remains the limit.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
 .../media/common/videobuf2/videobuf2-core.c   | 41 +++++++++++++++----
 .../media/common/videobuf2/videobuf2-v4l2.c   |  6 +--
 include/media/videobuf2-core.h                | 10 ++++-
 3 files changed, 44 insertions(+), 13 deletions(-)
  

Comments

Hans Verkuil Nov. 2, 2023, 8:17 a.m. UTC | #1
Hi Benjamin,

After a lot of testing yesterday I discovered that this patch introduces a
bug. After this bug, running the test-media script will result in a lot of
unbalanced counters messages:

[Wed Nov  1 16:40:48 2023] videobuf2_common: unbalanced counters for queue ffff888115a07f00, buffer 11:
[Wed Nov  1 16:40:48 2023] videobuf2_common:      buf_init: 1 buf_cleanup: 0
[Wed Nov  1 16:40:48 2023] videobuf2_common:      alloc: 1 put: 0
[Wed Nov  1 16:40:48 2023] videobuf2_common:      get_dmabuf: 0 num_users: 0

Apparently buf_init is called, but not buf_cleanup.

I also get loads of kmemleak reports:

unreferenced object 0xffff88800eae6800 (size 2048):
  comm "v4l2-compliance", pid 652, jiffies 4294937190 (age 149.650s)
  hex dump (first 32 bytes):
    e0 52 18 0c 81 88 ff ff 00 00 00 00 02 00 00 00  .R..............
    01 00 00 00 01 00 00 00 20 2f d3 f3 3e 00 00 00  ........ /..>...
  backtrace:
    [<ffffffffacbdb08b>] __kmalloc+0x4b/0x150
    [<ffffffffc01df77a>] __vb2_queue_alloc+0x11a/0xca0 [videobuf2_common]
    [<ffffffffc01e74f5>] vb2_core_reqbufs+0x735/0xfd0 [videobuf2_common]
    [<ffffffffc046ca71>] v4l2_m2m_ioctl_reqbufs+0xc1/0x1b0 [v4l2_mem2mem]
    [<ffffffffc0231520>] __video_do_ioctl+0x8d0/0xc20 [videodev]
    [<ffffffffc0232bcc>] video_usercopy+0x48c/0xd00 [videodev]
    [<ffffffffc021e2ff>] v4l2_ioctl+0x17f/0x1f0 [videodev]
    [<ffffffffacd758ce>] __do_compat_sys_ioctl+0x13e/0x1d0
    [<ffffffffae7df992>] __do_fast_syscall_32+0x62/0xe0
    [<ffffffffae7dfb4f>] do_fast_syscall_32+0x2f/0x70
    [<ffffffffaea012ed>] entry_SYSCALL_compat_after_hwframe+0x45/0x4d

Very likely the same issue.

Unfortunately, the build script does not yet check for issues like this,
you have to manually inspect the test-media logs (found in the logs directory
after the run). It's on my TODO list.

Regards,

	Hans

On 31/10/2023 17:30, Benjamin Gaignard wrote:
> Add 'max_num_buffers' field in vb2_queue struct to let drivers decide
> how many buffers could be stored in a queue.
> This require 'bufs' array to be allocated at queue init time and freed
> when releasing the queue.
> By default VB2_MAX_FRAME remains the limit.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> ---
>  .../media/common/videobuf2/videobuf2-core.c   | 41 +++++++++++++++----
>  .../media/common/videobuf2/videobuf2-v4l2.c   |  6 +--
>  include/media/videobuf2-core.h                | 10 ++++-
>  3 files changed, 44 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index c5c5ae4d213d..72ef7179d80a 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -416,7 +416,7 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
>   */
>  static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
>  {
> -	WARN_ON(index >= VB2_MAX_FRAME || q->bufs[index]);
> +	WARN_ON(index >= q->max_num_buffers || q->bufs[index]);
>  
>  	q->bufs[index] = vb;
>  	vb->index = index;
> @@ -449,9 +449,9 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>  	struct vb2_buffer *vb;
>  	int ret;
>  
> -	/* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */
> +	/* Ensure that the number of already queue + num_buffers is below q->max_num_buffers */
>  	num_buffers = min_t(unsigned int, num_buffers,
> -			    VB2_MAX_FRAME - q_num_buffers);
> +			    q->max_num_buffers - q_num_buffers);
>  
>  	for (buffer = 0; buffer < num_buffers; ++buffer) {
>  		/* Allocate vb2 buffer structures */
> @@ -813,7 +813,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  	unsigned plane_sizes[VB2_MAX_PLANES] = { };
>  	bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
>  	unsigned int i;
> -	int ret;
> +	int ret = 0;
>  
>  	if (q->streaming) {
>  		dprintk(q, 1, "streaming active\n");
> @@ -857,17 +857,22 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  	/*
>  	 * Make sure the requested values and current defaults are sane.
>  	 */
> -	WARN_ON(q->min_buffers_needed > VB2_MAX_FRAME);
>  	num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
> -	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
> +	num_buffers = min_t(unsigned int, num_buffers, q->max_num_buffers);
>  	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
>  	/*
>  	 * Set this now to ensure that drivers see the correct q->memory value
>  	 * in the queue_setup op.
>  	 */
>  	mutex_lock(&q->mmap_lock);
> +	if (!q->bufs)
> +		q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
> +	if (!q->bufs)
> +		ret = -ENOMEM;
>  	q->memory = memory;
>  	mutex_unlock(&q->mmap_lock);
> +	if (ret)
> +		return ret;
>  	set_queue_coherency(q, non_coherent_mem);
>  
>  	/*
> @@ -976,7 +981,7 @@ 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_bufs == VB2_MAX_FRAME) {
> +	if (q->num_buffers == q->max_num_buffers) {
>  		dprintk(q, 1, "maximum number of buffers already allocated\n");
>  		return -ENOBUFS;
>  	}
> @@ -993,7 +998,13 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  		 */
>  		mutex_lock(&q->mmap_lock);
>  		q->memory = memory;
> +		if (!q->bufs)
> +			q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
> +		if (!q->bufs)
> +			ret = -ENOMEM;
>  		mutex_unlock(&q->mmap_lock);
> +		if (ret)
> +			return ret;
>  		q->waiting_for_buffers = !q->is_output;
>  		set_queue_coherency(q, non_coherent_mem);
>  	} else {
> @@ -1005,7 +1016,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  			return -EINVAL;
>  	}
>  
> -	num_buffers = min(*count, VB2_MAX_FRAME - q_num_bufs);
> +	num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
>  
>  	if (requested_planes && requested_sizes) {
>  		num_planes = requested_planes;
> @@ -2465,6 +2476,12 @@ int vb2_core_queue_init(struct vb2_queue *q)
>  	/*
>  	 * Sanity check
>  	 */
> +	if (!q->max_num_buffers)
> +		q->max_num_buffers = VB2_MAX_FRAME;
> +
> +	/* The maximum is limited by offset cookie encoding pattern */
> +	q->max_num_buffers = min_t(unsigned int, q->max_num_buffers, MAX_BUFFER_INDEX);
> +
>  	if (WARN_ON(!q)			  ||
>  	    WARN_ON(!q->ops)		  ||
>  	    WARN_ON(!q->mem_ops)	  ||
> @@ -2474,6 +2491,10 @@ int vb2_core_queue_init(struct vb2_queue *q)
>  	    WARN_ON(!q->ops->buf_queue))
>  		return -EINVAL;
>  
> +	if (WARN_ON(q->max_num_buffers > MAX_BUFFER_INDEX) ||
> +	    WARN_ON(q->min_buffers_needed > q->max_num_buffers))
> +		return -EINVAL;
> +
>  	if (WARN_ON(q->requires_requests && !q->supports_requests))
>  		return -EINVAL;
>  
> @@ -2519,7 +2540,9 @@ 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, q->max_num_buffers);
> +	kfree(q->bufs);
> +	q->bufs = NULL;
>  	q->num_buffers = 0;
>  	mutex_unlock(&q->mmap_lock);
>  }
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 7d798fb15c0b..f3cf4b235c1f 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -627,7 +627,7 @@ struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
>  	 * This loop doesn't scale if there is a really large number of buffers.
>  	 * Maybe something more efficient will be needed in this case.
>  	 */
> -	for (i = 0; i < vb2_get_num_buffers(q); i++) {
> +	for (i = 0; i < q->max_num_buffers; i++) {
>  		vb2 = vb2_get_buffer(q, i);
>  
>  		if (!vb2)
> @@ -1142,7 +1142,7 @@ int _vb2_fop_release(struct file *file, struct mutex *lock)
>  
>  	if (lock)
>  		mutex_lock(lock);
> -	if (file->private_data == vdev->queue->owner) {
> +	if (!vdev->queue->owner || file->private_data == vdev->queue->owner) {
>  		vb2_queue_release(vdev->queue);
>  		vdev->queue->owner = NULL;
>  	}
> @@ -1270,7 +1270,7 @@ void vb2_video_unregister_device(struct video_device *vdev)
>  	 */
>  	get_device(&vdev->dev);
>  	video_unregister_device(vdev);
> -	if (vdev->queue && vdev->queue->owner) {
> +	if (vdev->queue) {
>  		struct mutex *lock = vdev->queue->lock ?
>  			vdev->queue->lock : vdev->lock;
>  
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 8f9d9e4af5b1..e77a397195f2 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -558,6 +558,7 @@ struct vb2_buf_ops {
>   * @dma_dir:	DMA mapping direction.
>   * @bufs:	videobuf2 buffer structures
>   * @num_buffers: number of allocated/used buffers
> + * @max_num_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.
>   * @owned_by_drv_count: number of buffers owned by the driver
> @@ -619,8 +620,9 @@ struct vb2_queue {
>  	struct mutex			mmap_lock;
>  	unsigned int			memory;
>  	enum dma_data_direction		dma_dir;
> -	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
> +	struct vb2_buffer		**bufs;
>  	unsigned int			num_buffers;
> +	unsigned int			max_num_buffers;
>  
>  	struct list_head		queued_list;
>  	unsigned int			queued_count;
> @@ -1248,6 +1250,12 @@ static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
>  static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
>  						unsigned int index)
>  {
> +	if (!q->bufs)
> +		return NULL;
> +
> +	if (index >= q->max_num_buffers)
> +		return NULL;
> +
>  	if (index < q->num_buffers)
>  		return q->bufs[index];
>  	return NULL;
  
Benjamin Gaignard Nov. 6, 2023, 2:29 p.m. UTC | #2
Le 02/11/2023 à 09:17, Hans Verkuil a écrit :
> Hi Benjamin,
>
> After a lot of testing yesterday I discovered that this patch introduces a
> bug. After this bug, running the test-media script will result in a lot of
> unbalanced counters messages:
>
> [Wed Nov  1 16:40:48 2023] videobuf2_common: unbalanced counters for queue ffff888115a07f00, buffer 11:
> [Wed Nov  1 16:40:48 2023] videobuf2_common:      buf_init: 1 buf_cleanup: 0
> [Wed Nov  1 16:40:48 2023] videobuf2_common:      alloc: 1 put: 0
> [Wed Nov  1 16:40:48 2023] videobuf2_common:      get_dmabuf: 0 num_users: 0
>
> Apparently buf_init is called, but not buf_cleanup.
>
> I also get loads of kmemleak reports:
>
> unreferenced object 0xffff88800eae6800 (size 2048):
>    comm "v4l2-compliance", pid 652, jiffies 4294937190 (age 149.650s)
>    hex dump (first 32 bytes):
>      e0 52 18 0c 81 88 ff ff 00 00 00 00 02 00 00 00  .R..............
>      01 00 00 00 01 00 00 00 20 2f d3 f3 3e 00 00 00  ........ /..>...
>    backtrace:
>      [<ffffffffacbdb08b>] __kmalloc+0x4b/0x150
>      [<ffffffffc01df77a>] __vb2_queue_alloc+0x11a/0xca0 [videobuf2_common]
>      [<ffffffffc01e74f5>] vb2_core_reqbufs+0x735/0xfd0 [videobuf2_common]
>      [<ffffffffc046ca71>] v4l2_m2m_ioctl_reqbufs+0xc1/0x1b0 [v4l2_mem2mem]
>      [<ffffffffc0231520>] __video_do_ioctl+0x8d0/0xc20 [videodev]
>      [<ffffffffc0232bcc>] video_usercopy+0x48c/0xd00 [videodev]
>      [<ffffffffc021e2ff>] v4l2_ioctl+0x17f/0x1f0 [videodev]
>      [<ffffffffacd758ce>] __do_compat_sys_ioctl+0x13e/0x1d0
>      [<ffffffffae7df992>] __do_fast_syscall_32+0x62/0xe0
>      [<ffffffffae7dfb4f>] do_fast_syscall_32+0x2f/0x70
>      [<ffffffffaea012ed>] entry_SYSCALL_compat_after_hwframe+0x45/0x4d
>
> Very likely the same issue.
>
> Unfortunately, the build script does not yet check for issues like this,
> you have to manually inspect the test-media logs (found in the logs directory
> after the run). It's on my TODO list.

The issue is in vb2_core_queue_release(), the patch shouldn't change
__vb2_queue_free() second parameter.
When removing this change, unbalanced messages disappear.

Regards,
Benjamin

>
> Regards,
>
> 	Hans
>
> On 31/10/2023 17:30, Benjamin Gaignard wrote:
>> Add 'max_num_buffers' field in vb2_queue struct to let drivers decide
>> how many buffers could be stored in a queue.
>> This require 'bufs' array to be allocated at queue init time and freed
>> when releasing the queue.
>> By default VB2_MAX_FRAME remains the limit.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
>> ---
>>   .../media/common/videobuf2/videobuf2-core.c   | 41 +++++++++++++++----
>>   .../media/common/videobuf2/videobuf2-v4l2.c   |  6 +--
>>   include/media/videobuf2-core.h                | 10 ++++-
>>   3 files changed, 44 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>> index c5c5ae4d213d..72ef7179d80a 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>> @@ -416,7 +416,7 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
>>    */
>>   static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
>>   {
>> -	WARN_ON(index >= VB2_MAX_FRAME || q->bufs[index]);
>> +	WARN_ON(index >= q->max_num_buffers || q->bufs[index]);
>>   
>>   	q->bufs[index] = vb;
>>   	vb->index = index;
>> @@ -449,9 +449,9 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>   	struct vb2_buffer *vb;
>>   	int ret;
>>   
>> -	/* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */
>> +	/* Ensure that the number of already queue + num_buffers is below q->max_num_buffers */
>>   	num_buffers = min_t(unsigned int, num_buffers,
>> -			    VB2_MAX_FRAME - q_num_buffers);
>> +			    q->max_num_buffers - q_num_buffers);
>>   
>>   	for (buffer = 0; buffer < num_buffers; ++buffer) {
>>   		/* Allocate vb2 buffer structures */
>> @@ -813,7 +813,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>>   	unsigned plane_sizes[VB2_MAX_PLANES] = { };
>>   	bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
>>   	unsigned int i;
>> -	int ret;
>> +	int ret = 0;
>>   
>>   	if (q->streaming) {
>>   		dprintk(q, 1, "streaming active\n");
>> @@ -857,17 +857,22 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>>   	/*
>>   	 * Make sure the requested values and current defaults are sane.
>>   	 */
>> -	WARN_ON(q->min_buffers_needed > VB2_MAX_FRAME);
>>   	num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
>> -	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
>> +	num_buffers = min_t(unsigned int, num_buffers, q->max_num_buffers);
>>   	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
>>   	/*
>>   	 * Set this now to ensure that drivers see the correct q->memory value
>>   	 * in the queue_setup op.
>>   	 */
>>   	mutex_lock(&q->mmap_lock);
>> +	if (!q->bufs)
>> +		q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
>> +	if (!q->bufs)
>> +		ret = -ENOMEM;
>>   	q->memory = memory;
>>   	mutex_unlock(&q->mmap_lock);
>> +	if (ret)
>> +		return ret;
>>   	set_queue_coherency(q, non_coherent_mem);
>>   
>>   	/*
>> @@ -976,7 +981,7 @@ 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_bufs == VB2_MAX_FRAME) {
>> +	if (q->num_buffers == q->max_num_buffers) {
>>   		dprintk(q, 1, "maximum number of buffers already allocated\n");
>>   		return -ENOBUFS;
>>   	}
>> @@ -993,7 +998,13 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>   		 */
>>   		mutex_lock(&q->mmap_lock);
>>   		q->memory = memory;
>> +		if (!q->bufs)
>> +			q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
>> +		if (!q->bufs)
>> +			ret = -ENOMEM;
>>   		mutex_unlock(&q->mmap_lock);
>> +		if (ret)
>> +			return ret;
>>   		q->waiting_for_buffers = !q->is_output;
>>   		set_queue_coherency(q, non_coherent_mem);
>>   	} else {
>> @@ -1005,7 +1016,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>   			return -EINVAL;
>>   	}
>>   
>> -	num_buffers = min(*count, VB2_MAX_FRAME - q_num_bufs);
>> +	num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
>>   
>>   	if (requested_planes && requested_sizes) {
>>   		num_planes = requested_planes;
>> @@ -2465,6 +2476,12 @@ int vb2_core_queue_init(struct vb2_queue *q)
>>   	/*
>>   	 * Sanity check
>>   	 */
>> +	if (!q->max_num_buffers)
>> +		q->max_num_buffers = VB2_MAX_FRAME;
>> +
>> +	/* The maximum is limited by offset cookie encoding pattern */
>> +	q->max_num_buffers = min_t(unsigned int, q->max_num_buffers, MAX_BUFFER_INDEX);
>> +
>>   	if (WARN_ON(!q)			  ||
>>   	    WARN_ON(!q->ops)		  ||
>>   	    WARN_ON(!q->mem_ops)	  ||
>> @@ -2474,6 +2491,10 @@ int vb2_core_queue_init(struct vb2_queue *q)
>>   	    WARN_ON(!q->ops->buf_queue))
>>   		return -EINVAL;
>>   
>> +	if (WARN_ON(q->max_num_buffers > MAX_BUFFER_INDEX) ||
>> +	    WARN_ON(q->min_buffers_needed > q->max_num_buffers))
>> +		return -EINVAL;
>> +
>>   	if (WARN_ON(q->requires_requests && !q->supports_requests))
>>   		return -EINVAL;
>>   
>> @@ -2519,7 +2540,9 @@ 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, q->max_num_buffers);
>> +	kfree(q->bufs);
>> +	q->bufs = NULL;
>>   	q->num_buffers = 0;
>>   	mutex_unlock(&q->mmap_lock);
>>   }
>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> index 7d798fb15c0b..f3cf4b235c1f 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> @@ -627,7 +627,7 @@ struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
>>   	 * This loop doesn't scale if there is a really large number of buffers.
>>   	 * Maybe something more efficient will be needed in this case.
>>   	 */
>> -	for (i = 0; i < vb2_get_num_buffers(q); i++) {
>> +	for (i = 0; i < q->max_num_buffers; i++) {
>>   		vb2 = vb2_get_buffer(q, i);
>>   
>>   		if (!vb2)
>> @@ -1142,7 +1142,7 @@ int _vb2_fop_release(struct file *file, struct mutex *lock)
>>   
>>   	if (lock)
>>   		mutex_lock(lock);
>> -	if (file->private_data == vdev->queue->owner) {
>> +	if (!vdev->queue->owner || file->private_data == vdev->queue->owner) {
>>   		vb2_queue_release(vdev->queue);
>>   		vdev->queue->owner = NULL;
>>   	}
>> @@ -1270,7 +1270,7 @@ void vb2_video_unregister_device(struct video_device *vdev)
>>   	 */
>>   	get_device(&vdev->dev);
>>   	video_unregister_device(vdev);
>> -	if (vdev->queue && vdev->queue->owner) {
>> +	if (vdev->queue) {
>>   		struct mutex *lock = vdev->queue->lock ?
>>   			vdev->queue->lock : vdev->lock;
>>   
>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>> index 8f9d9e4af5b1..e77a397195f2 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>> @@ -558,6 +558,7 @@ struct vb2_buf_ops {
>>    * @dma_dir:	DMA mapping direction.
>>    * @bufs:	videobuf2 buffer structures
>>    * @num_buffers: number of allocated/used buffers
>> + * @max_num_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.
>>    * @owned_by_drv_count: number of buffers owned by the driver
>> @@ -619,8 +620,9 @@ struct vb2_queue {
>>   	struct mutex			mmap_lock;
>>   	unsigned int			memory;
>>   	enum dma_data_direction		dma_dir;
>> -	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
>> +	struct vb2_buffer		**bufs;
>>   	unsigned int			num_buffers;
>> +	unsigned int			max_num_buffers;
>>   
>>   	struct list_head		queued_list;
>>   	unsigned int			queued_count;
>> @@ -1248,6 +1250,12 @@ static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
>>   static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
>>   						unsigned int index)
>>   {
>> +	if (!q->bufs)
>> +		return NULL;
>> +
>> +	if (index >= q->max_num_buffers)
>> +		return NULL;
>> +
>>   	if (index < q->num_buffers)
>>   		return q->bufs[index];
>>   	return NULL;
  

Patch

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index c5c5ae4d213d..72ef7179d80a 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -416,7 +416,7 @@  static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
  */
 static void vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, unsigned int index)
 {
-	WARN_ON(index >= VB2_MAX_FRAME || q->bufs[index]);
+	WARN_ON(index >= q->max_num_buffers || q->bufs[index]);
 
 	q->bufs[index] = vb;
 	vb->index = index;
@@ -449,9 +449,9 @@  static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
 	struct vb2_buffer *vb;
 	int ret;
 
-	/* Ensure that q->num_buffers+num_buffers is below VB2_MAX_FRAME */
+	/* Ensure that the number of already queue + num_buffers is below q->max_num_buffers */
 	num_buffers = min_t(unsigned int, num_buffers,
-			    VB2_MAX_FRAME - q_num_buffers);
+			    q->max_num_buffers - q_num_buffers);
 
 	for (buffer = 0; buffer < num_buffers; ++buffer) {
 		/* Allocate vb2 buffer structures */
@@ -813,7 +813,7 @@  int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
 	bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
 	unsigned int i;
-	int ret;
+	int ret = 0;
 
 	if (q->streaming) {
 		dprintk(q, 1, "streaming active\n");
@@ -857,17 +857,22 @@  int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	/*
 	 * Make sure the requested values and current defaults are sane.
 	 */
-	WARN_ON(q->min_buffers_needed > VB2_MAX_FRAME);
 	num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
-	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
+	num_buffers = min_t(unsigned int, num_buffers, q->max_num_buffers);
 	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
 	/*
 	 * Set this now to ensure that drivers see the correct q->memory value
 	 * in the queue_setup op.
 	 */
 	mutex_lock(&q->mmap_lock);
+	if (!q->bufs)
+		q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
+	if (!q->bufs)
+		ret = -ENOMEM;
 	q->memory = memory;
 	mutex_unlock(&q->mmap_lock);
+	if (ret)
+		return ret;
 	set_queue_coherency(q, non_coherent_mem);
 
 	/*
@@ -976,7 +981,7 @@  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_bufs == VB2_MAX_FRAME) {
+	if (q->num_buffers == q->max_num_buffers) {
 		dprintk(q, 1, "maximum number of buffers already allocated\n");
 		return -ENOBUFS;
 	}
@@ -993,7 +998,13 @@  int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 		 */
 		mutex_lock(&q->mmap_lock);
 		q->memory = memory;
+		if (!q->bufs)
+			q->bufs = kcalloc(q->max_num_buffers, sizeof(*q->bufs), GFP_KERNEL);
+		if (!q->bufs)
+			ret = -ENOMEM;
 		mutex_unlock(&q->mmap_lock);
+		if (ret)
+			return ret;
 		q->waiting_for_buffers = !q->is_output;
 		set_queue_coherency(q, non_coherent_mem);
 	} else {
@@ -1005,7 +1016,7 @@  int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 			return -EINVAL;
 	}
 
-	num_buffers = min(*count, VB2_MAX_FRAME - q_num_bufs);
+	num_buffers = min(*count, q->max_num_buffers - q_num_bufs);
 
 	if (requested_planes && requested_sizes) {
 		num_planes = requested_planes;
@@ -2465,6 +2476,12 @@  int vb2_core_queue_init(struct vb2_queue *q)
 	/*
 	 * Sanity check
 	 */
+	if (!q->max_num_buffers)
+		q->max_num_buffers = VB2_MAX_FRAME;
+
+	/* The maximum is limited by offset cookie encoding pattern */
+	q->max_num_buffers = min_t(unsigned int, q->max_num_buffers, MAX_BUFFER_INDEX);
+
 	if (WARN_ON(!q)			  ||
 	    WARN_ON(!q->ops)		  ||
 	    WARN_ON(!q->mem_ops)	  ||
@@ -2474,6 +2491,10 @@  int vb2_core_queue_init(struct vb2_queue *q)
 	    WARN_ON(!q->ops->buf_queue))
 		return -EINVAL;
 
+	if (WARN_ON(q->max_num_buffers > MAX_BUFFER_INDEX) ||
+	    WARN_ON(q->min_buffers_needed > q->max_num_buffers))
+		return -EINVAL;
+
 	if (WARN_ON(q->requires_requests && !q->supports_requests))
 		return -EINVAL;
 
@@ -2519,7 +2540,9 @@  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, q->max_num_buffers);
+	kfree(q->bufs);
+	q->bufs = NULL;
 	q->num_buffers = 0;
 	mutex_unlock(&q->mmap_lock);
 }
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 7d798fb15c0b..f3cf4b235c1f 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -627,7 +627,7 @@  struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
 	 * This loop doesn't scale if there is a really large number of buffers.
 	 * Maybe something more efficient will be needed in this case.
 	 */
-	for (i = 0; i < vb2_get_num_buffers(q); i++) {
+	for (i = 0; i < q->max_num_buffers; i++) {
 		vb2 = vb2_get_buffer(q, i);
 
 		if (!vb2)
@@ -1142,7 +1142,7 @@  int _vb2_fop_release(struct file *file, struct mutex *lock)
 
 	if (lock)
 		mutex_lock(lock);
-	if (file->private_data == vdev->queue->owner) {
+	if (!vdev->queue->owner || file->private_data == vdev->queue->owner) {
 		vb2_queue_release(vdev->queue);
 		vdev->queue->owner = NULL;
 	}
@@ -1270,7 +1270,7 @@  void vb2_video_unregister_device(struct video_device *vdev)
 	 */
 	get_device(&vdev->dev);
 	video_unregister_device(vdev);
-	if (vdev->queue && vdev->queue->owner) {
+	if (vdev->queue) {
 		struct mutex *lock = vdev->queue->lock ?
 			vdev->queue->lock : vdev->lock;
 
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 8f9d9e4af5b1..e77a397195f2 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -558,6 +558,7 @@  struct vb2_buf_ops {
  * @dma_dir:	DMA mapping direction.
  * @bufs:	videobuf2 buffer structures
  * @num_buffers: number of allocated/used buffers
+ * @max_num_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.
  * @owned_by_drv_count: number of buffers owned by the driver
@@ -619,8 +620,9 @@  struct vb2_queue {
 	struct mutex			mmap_lock;
 	unsigned int			memory;
 	enum dma_data_direction		dma_dir;
-	struct vb2_buffer		*bufs[VB2_MAX_FRAME];
+	struct vb2_buffer		**bufs;
 	unsigned int			num_buffers;
+	unsigned int			max_num_buffers;
 
 	struct list_head		queued_list;
 	unsigned int			queued_count;
@@ -1248,6 +1250,12 @@  static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
 static inline struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q,
 						unsigned int index)
 {
+	if (!q->bufs)
+		return NULL;
+
+	if (index >= q->max_num_buffers)
+		return NULL;
+
 	if (index < q->num_buffers)
 		return q->bufs[index];
 	return NULL;