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Message-ID: <b8480c15-3390-b57f-b2c5-9d9e0f2c1382@collabora.com>
Date:   Thu, 31 Aug 2023 14:06:42 +0200
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Subject: Re: [PATCH v5 02/10] media: videobuf2: Access vb2_queue bufs array
 through helper functions
Content-Language: en-US
To:     Hans Verkuil <hverkuil-cisco@xs4all.nl>, mchehab@kernel.org,
        tfiga@chromium.org, m.szyprowski@samsung.com, ming.qian@nxp.com,
        ezequiel@vanguardiasur.com.ar, p.zabel@pengutronix.de,
        gregkh@linuxfoundation.org, nicolas.dufresne@collabora.com
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org,
        linux-rockchip@lists.infradead.org, linux-staging@lists.linux.dev,
        kernel@collabora.com
References: <20230824092133.39510-1-benjamin.gaignard@collabora.com>
 <20230824092133.39510-3-benjamin.gaignard@collabora.com>
 <397c6779-6153-5df2-a9f7-708bb7fcf58d@xs4all.nl>
 <73e3e87b-78d6-13b2-8a20-09a75d5f23d0@collabora.com>
 <ac1a0848-8b95-0141-c590-f29d74e8c9da@xs4all.nl>
 <07c2de04-f4a7-71e2-ef41-64e87495ff42@collabora.com>
 <c927dccb-9915-38dc-a522-f3d4a9755abf@xs4all.nl>
From:   Benjamin Gaignard <benjamin.gaignard@collabora.com>
In-Reply-To: <c927dccb-9915-38dc-a522-f3d4a9755abf@xs4all.nl>
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Le 31/08/2023 à 12:22, Hans Verkuil a écrit :
> On 31/08/2023 09:54, Benjamin Gaignard wrote:
>> Le 30/08/2023 à 18:36, Hans Verkuil a écrit :
>>> On 30/08/2023 18:24, Benjamin Gaignard wrote:
>>>> Le 30/08/2023 à 15:23, Hans Verkuil a écrit :
>>>>> On 24/08/2023 11:21, Benjamin Gaignard wrote:
>>>>>> The first step before changing how vb2 buffers are stored into queue
>>>>>> is to avoid direct access to bufs arrays.
>>>>>>
>>>>>> This patch adds 2 helpers functions to add and remove vb2 buffers
>>>>>> from a queue. With these 2 and vb2_get_buffer(), bufs field of
>>>>>> struct vb2_queue becomes like a private member of the structure.
>>>>>>
>>>>>> After each call to vb2_get_buffer() we need to be sure that we get
>>>>>> a valid pointer so check the return value of all of them.
>>>>>>
>>>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>>>>>
>>>>>> # Conflicts:
>>>>>> #    drivers/media/common/videobuf2/videobuf2-core.c
>>>>>> ---
>>>>>>     .../media/common/videobuf2/videobuf2-core.c   | 203 ++++++++++++++----
>>>>>>     .../media/common/videobuf2/videobuf2-v4l2.c   |  28 ++-
>>>>>>     drivers/media/platform/amphion/vpu_dbg.c      |  22 +-
>>>>>>     .../platform/mediatek/jpeg/mtk_jpeg_core.c    |   6 +-
>>>>>>     .../vcodec/decoder/vdec/vdec_vp9_req_lat_if.c |   2 +-
>>>>>>     drivers/media/platform/st/sti/hva/hva-v4l2.c  |   4 +
>>>>>>     drivers/media/test-drivers/visl/visl-dec.c    |  28 ++-
>>>>>>     .../staging/media/atomisp/pci/atomisp_ioctl.c |   2 +-
>>>>>>     8 files changed, 230 insertions(+), 65 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>>>>>> index e06905533ef4..8aa13591b782 100644
>>>>>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>>>>>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>>>>>> @@ -403,6 +403,37 @@ static void init_buffer_cache_hints(struct vb2_queue *q, struct vb2_buffer *vb)
>>>>>>             vb->skip_cache_sync_on_finish = 1;
>>>>>>     }
>>>>>>     +/**
>>>>>> + * vb2_queue_add_buffer() - add a buffer to a queue
>>>>>> + * @q:    pointer to &struct vb2_queue with videobuf2 queue.
>>>>>> + * @vb:    pointer to &struct vb2_buffer to be added to the queue.
>>>>>> + * @index: index where add vb2_buffer in the queue
>>>>>> + */
>>>>>> +static bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *vb, int index)
>>>>>> +{
>>>>>> +    if (index < VB2_MAX_FRAME && !q->bufs[index]) {
>>>>>> +        q->bufs[index] = vb;
>>>>>> +        vb->index = index;
>>>>>> +        vb->vb2_queue = q;
>>>>>> +        return true;
>>>>>> +    }
>>>>>> +
>>>>>> +    return false;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * vb2_queue_remove_buffer() - remove a buffer from a queue
>>>>>> + * @q:    pointer to &struct vb2_queue with videobuf2 queue.
>>>>>> + * @vb:    pointer to &struct vb2_buffer to be removed from the queue.
>>>>>> + */
>>>>>> +static void vb2_queue_remove_buffer(struct vb2_queue *q, struct vb2_buffer *vb)
>>>>>> +{
>>>>>> +    if (vb->index < VB2_MAX_FRAME) {
>>>>>> +        q->bufs[vb->index] = NULL;
>>>>>> +        vb->vb2_queue = NULL;
>>>>>> +    }
>>>>>> +}
>>>>>> +
>>>>>>     /*
>>>>>>      * __vb2_queue_alloc() - allocate vb2 buffer structures and (for MMAP type)
>>>>>>      * video buffer memory for all buffers/planes on the queue and initializes the
>>>>>> @@ -431,9 +462,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>>             }
>>>>>>               vb->state = VB2_BUF_STATE_DEQUEUED;
>>>>>> -        vb->vb2_queue = q;
>>>>>>             vb->num_planes = num_planes;
>>>>>> -        vb->index = q->num_buffers + buffer;
>>>>>>             vb->type = q->type;
>>>>>>             vb->memory = memory;
>>>>>>             init_buffer_cache_hints(q, vb);
>>>>>> @@ -443,7 +472,11 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>>             }
>>>>>>             call_void_bufop(q, init_buffer, vb);
>>>>>>     -        q->bufs[vb->index] = vb;
>>>>>> +        if (!vb2_queue_add_buffer(q, vb, q->num_buffers + buffer)) {
>>>>>> +            dprintk(q, 1, "failed adding buffer %d to queue\n", buffer);
>>>>>> +            kfree(vb);
>>>>>> +            break;
>>>>>> +        }
>>>>>>               /* Allocate video buffer memory for the MMAP type */
>>>>>>             if (memory == VB2_MEMORY_MMAP) {
>>>>>> @@ -451,7 +484,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>>                 if (ret) {
>>>>>>                     dprintk(q, 1, "failed allocating memory for buffer %d\n",
>>>>>>                         buffer);
>>>>>> -                q->bufs[vb->index] = NULL;
>>>>>> +                vb2_queue_remove_buffer(q, vb);
>>>>>>                     kfree(vb);
>>>>>>                     break;
>>>>>>                 }
>>>>>> @@ -466,7 +499,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
>>>>>>                     dprintk(q, 1, "buffer %d %p initialization failed\n",
>>>>>>                         buffer, vb);
>>>>>>                     __vb2_buf_mem_free(vb);
>>>>>> -                q->bufs[vb->index] = NULL;
>>>>>> +                vb2_queue_remove_buffer(q, vb);
>>>>>>                     kfree(vb);
>>>>>>                     break;
>>>>>>                 }
>>>>>> @@ -489,7 +522,7 @@ static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
>>>>>>           for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>>>>>>              ++buffer) {
>>>>>> -        vb = q->bufs[buffer];
>>>>>> +        vb = vb2_get_buffer(q, buffer);
>>>>>>             if (!vb)
>>>>>>                 continue;
>>>>>>     @@ -517,7 +550,7 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>>>>>>         /* 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 = q->bufs[buffer];
>>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>>>               if (vb && vb->planes[0].mem_priv)
>>>>>>                 call_void_vb_qop(vb, buf_cleanup, vb);
>>>>>> @@ -557,15 +590,20 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>>>>>>             q->cnt_unprepare_streaming = 0;
>>>>>>         }
>>>>>>         for (buffer = 0; buffer < q->num_buffers; ++buffer) {
>>>>>> -        struct vb2_buffer *vb = q->bufs[buffer];
>>>>>> -        bool unbalanced = vb->cnt_mem_alloc != vb->cnt_mem_put ||
>>>>>> -                  vb->cnt_mem_prepare != vb->cnt_mem_finish ||
>>>>>> -                  vb->cnt_mem_get_userptr != vb->cnt_mem_put_userptr ||
>>>>>> -                  vb->cnt_mem_attach_dmabuf != vb->cnt_mem_detach_dmabuf ||
>>>>>> -                  vb->cnt_mem_map_dmabuf != vb->cnt_mem_unmap_dmabuf ||
>>>>>> -                  vb->cnt_buf_queue != vb->cnt_buf_done ||
>>>>>> -                  vb->cnt_buf_prepare != vb->cnt_buf_finish ||
>>>>>> -                  vb->cnt_buf_init != vb->cnt_buf_cleanup;
>>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>>> +        bool unbalanced;
>>>>>> +
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        unbalanced = vb->cnt_mem_alloc != vb->cnt_mem_put ||
>>>>>> +                 vb->cnt_mem_prepare != vb->cnt_mem_finish ||
>>>>>> +                 vb->cnt_mem_get_userptr != vb->cnt_mem_put_userptr ||
>>>>>> +                 vb->cnt_mem_attach_dmabuf != vb->cnt_mem_detach_dmabuf ||
>>>>>> +                 vb->cnt_mem_map_dmabuf != vb->cnt_mem_unmap_dmabuf ||
>>>>>> +                 vb->cnt_buf_queue != vb->cnt_buf_done ||
>>>>>> +                 vb->cnt_buf_prepare != vb->cnt_buf_finish ||
>>>>>> +                 vb->cnt_buf_init != vb->cnt_buf_cleanup;
>>>>>>               if (unbalanced || debug) {
>>>>> I think we should drop the '|| debug' part. It is already annoying today to see these
>>>>> messages when the debug parameter is > 0, and now the number of buffers is still
>>>>> fairly small. But if we allow a lot more buffers, then this will really spam the
>>>>> kernel log.
>>>>>
>>>>> I think this should be dropped, and we only report unbalanced buffers.
>>>>>
>>>>> And another optimization is to only report the unbalanced counters. Right now
>>>>> it reports all counters, but it is again too much spamming of the kernel log.
>>>>>
>>>>> I think this change can be done as a separate patch before this patch.
>>>>> That way it can be picked up separately from the other changes in this series.
>>>>>
>>>>>>                 pr_info("   counters for queue %p, buffer %d:%s\n",
>>>>>> @@ -597,8 +635,13 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>>>>>>         /* Free vb2 buffers */
>>>>>>         for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
>>>>>>              ++buffer) {
>>>>>> -        kfree(q->bufs[buffer]);
>>>>>> -        q->bufs[buffer] = NULL;
>>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>>> +
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        vb2_queue_remove_buffer(q, vb);
>>>>>> +        kfree(vb);
>>>>>>         }
>>>>>>           q->num_buffers -= buffers;
>>>>>> @@ -634,7 +677,12 @@ static bool __buffers_in_use(struct vb2_queue *q)
>>>>>>     {
>>>>>>         unsigned int buffer;
>>>>>>         for (buffer = 0; buffer < q->num_buffers; ++buffer) {
>>>>>> -        if (vb2_buffer_in_use(q, q->bufs[buffer]))
>>>>>> +        struct vb2_buffer *vb = vb2_get_buffer(q, buffer);
>>>>>> +
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        if (vb2_buffer_in_use(q, vb))
>>>>>>                 return true;
>>>>>>         }
>>>>>>         return false;
>>>>>> @@ -642,7 +690,10 @@ static bool __buffers_in_use(struct vb2_queue *q)
>>>>>>       void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb)
>>>>>>     {
>>>>>> -    call_void_bufop(q, fill_user_buffer, q->bufs[index], pb);
>>>>>> +    struct vb2_buffer *vb = vb2_get_buffer(q, index);
>>>>>> +
>>>>>> +    if (vb)
>>>>>> +        call_void_bufop(q, fill_user_buffer, vb, pb);
>>>>> I think that rather than passing the index (that then has to be verified)
>>>>> it is better to pass the vb2_buffer pointer directly and leave it up to
>>>>> the caller to do the index verification.
>>>>>
>>>>> Another option is to drop this function altogether and let the called
>>>>> call the fill_user_buffer function. Either works for me.
>>>>>
>>>>>>     }
>>>>>>     EXPORT_SYMBOL_GPL(vb2_core_querybuf);
>>>>>>     @@ -1553,7 +1604,13 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
>>>>> Here too it is better to pass the vb2_buffer pointer instead of an index.
>>>>>
>>>>> This function assumes that the index is valid, so the called actually does the
>>>>> validation. Passing the vb pointer instead of the index makes more sense
>>>>> in this new situation.
>>>>>
>>>>> This is also true for two other core functions: vb2_core_qbuf and vb2_core_expbuf.
>>>>>
>>>>>>         struct vb2_buffer *vb;
>>>>>>         int ret;
>>>>>>     -    vb = q->bufs[index];
>>>>>> +    vb = vb2_get_buffer(q, index);
>>>>>> +
>>>>>> +    if (!vb) {
>>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +        return -EINVAL;
>>>>>> +    }
>>>>> Changing that avoids having to add this check, so it simplifies the code.
>>>>>
>>>>> I think that this change can be done in a separate patch before this one.
>>>>>
>>>>> It makes sense to apply that regardless of the remainder of this series.
>>>>>
>>>>>> +
>>>>>>         if (vb->state != VB2_BUF_STATE_DEQUEUED) {
>>>>>>             dprintk(q, 1, "invalid buffer state %s\n",
>>>>>>                 vb2_state_name(vb->state));
>>>>>> @@ -1624,7 +1681,11 @@ static int vb2_start_streaming(struct vb2_queue *q)
>>>>>>              * correctly return them to vb2.
>>>>>>              */
>>>>>>             for (i = 0; i < q->num_buffers; ++i) {
>>>>>> -            vb = q->bufs[i];
>>>>>> +            vb = vb2_get_buffer(q, i);
>>>>>> +
>>>>>> +            if (!vb)
>>>>>> +                continue;
>>>>>> +
>>>>>>                 if (vb->state == VB2_BUF_STATE_ACTIVE)
>>>>>>                     vb2_buffer_done(vb, VB2_BUF_STATE_QUEUED);
>>>>>>             }
>>>>>> @@ -1652,7 +1713,12 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
>>>>>>             return -EIO;
>>>>>>         }
>>>>>>     -    vb = q->bufs[index];
>>>>>> +    vb = vb2_get_buffer(q, index);
>>>>>> +
>>>>>> +    if (!vb) {
>>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +        return -EINVAL;
>>>>>> +    }
>>>>>>           if (!req && vb->state != VB2_BUF_STATE_IN_REQUEST &&
>>>>>>             q->requires_requests) {
>>>>>> @@ -2028,12 +2094,18 @@ 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 < q->num_buffers; ++i)
>>>>>> -            if (q->bufs[i]->state == VB2_BUF_STATE_ACTIVE) {
>>>>>> +        for (i = 0; i < q->num_buffers; ++i) {
>>>>>> +            struct vb2_buffer *vb = vb2_get_buffer(q, i);
>>>>>> +
>>>>>> +            if (!vb)
>>>>>> +                continue;
>>>>>> +
>>>>>> +            if (vb->state == VB2_BUF_STATE_ACTIVE) {
>>>>>>                     pr_warn("driver bug: stop_streaming operation is leaving buf %p in active state\n",
>>>>>> -                    q->bufs[i]);
>>>>>> -                vb2_buffer_done(q->bufs[i], VB2_BUF_STATE_ERROR);
>>>>>> +                    vb);
>>>>>> +                vb2_buffer_done(vb, VB2_BUF_STATE_ERROR);
>>>>>>                 }
>>>>>> +        }
>>>>>>             /* Must be zero now */
>>>>>>             WARN_ON(atomic_read(&q->owned_by_drv_count));
>>>>>>         }
>>>>>> @@ -2067,9 +2139,14 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
>>>>>>          * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
>>>>>>          */
>>>>>>         for (i = 0; i < q->num_buffers; ++i) {
>>>>>> -        struct vb2_buffer *vb = q->bufs[i];
>>>>>> -        struct media_request *req = vb->req_obj.req;
>>>>>> +        struct vb2_buffer *vb;
>>>>>> +        struct media_request *req;
>>>>>> +
>>>>>> +        vb = vb2_get_buffer(q, i);
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>>     +        req = vb->req_obj.req;
>>>>>>             /*
>>>>>>              * If a request is associated with this buffer, then
>>>>>>              * call buf_request_cancel() to give the driver to complete()
>>>>>> @@ -2219,7 +2296,10 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
>>>>>>         buffer = (off >> (PLANE_INDEX_SHIFT + PAGE_SHIFT)) & MAX_BUFFERS;
>>>>>>         plane = (off >> PAGE_SHIFT) & PLANE_INDEX_MASK;
>>>>>>     -    vb = q->bufs[buffer];
>>>>>> +    vb = vb2_get_buffer(q, buffer);
>>>>>> +    if (!vb)
>>>>>> +        return -EINVAL;
>>>>>> +
>>>>>>         if (vb->planes[plane].m.offset == off) {
>>>>>>             *_buffer = buffer;
>>>>>>             *_plane = plane;
>>>>>> @@ -2262,7 +2342,12 @@ int vb2_core_expbuf(struct vb2_queue *q, int *fd, unsigned int type,
>>>>>>             return -EINVAL;
>>>>>>         }
>>>>>>     -    vb = q->bufs[index];
>>>>>> +    vb = vb2_get_buffer(q, index);
>>>>>> +
>>>>>> +    if (!vb) {
>>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +        return -EINVAL;
>>>>>> +    }
>>>>>>           if (plane >= vb->num_planes) {
>>>>>>             dprintk(q, 1, "buffer plane out of range\n");
>>>>>> @@ -2339,7 +2424,13 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
>>>>>>         if (ret)
>>>>>>             goto unlock;
>>>>>>     -    vb = q->bufs[buffer];
>>>>>> +    vb = vb2_get_buffer(q, buffer);
>>>>>> +
>>>>>> +    if (!vb) {
>>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +        ret = -EINVAL;
>>>>>> +        goto unlock;
>>>>>> +    }
>>>>>>           /*
>>>>>>          * MMAP requires page_aligned buffers.
>>>>>> @@ -2396,7 +2487,12 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
>>>>>>         if (ret)
>>>>>>             goto unlock;
>>>>>>     -    vb = q->bufs[buffer];
>>>>>> +    vb = vb2_get_buffer(q, buffer);
>>>>>> +    if (!vb) {
>>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +        ret = -EINVAL;
>>>>>> +        goto unlock;
>>>>>> +    }
>>>>>>           vaddr = vb2_plane_vaddr(vb, plane);
>>>>>>         mutex_unlock(&q->mmap_lock);
>>>>>> @@ -2625,6 +2721,7 @@ struct vb2_fileio_data {
>>>>>>     static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>>>>     {
>>>>>>         struct vb2_fileio_data *fileio;
>>>>>> +    struct vb2_buffer *vb;
>>>>>>         int i, ret;
>>>>>>         unsigned int count = 0;
>>>>>>     @@ -2679,7 +2776,13 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>>>>          * Check if plane_count is correct
>>>>>>          * (multiplane buffers are not supported).
>>>>>>          */
>>>>>> -    if (q->bufs[0]->num_planes != 1) {
>>>>>> +    vb = vb2_get_buffer(q, 0);
>>>>>> +    if (!vb) {
>>>>>> +        ret = -EBUSY;
>>>>>> +        goto err_reqbufs;
>>>>>> +    }
>>>>> This cannot happen. These fileio helper functions implement the read() support
>>>>> and all the buffer allocation happens here. Userspace can never add or delete
>>>>> buffers later, so there will never be holes. It is safe to assume that
>>>>> vb2_get_buffer(q, i) will always return a valid vb pointer for i in the range
>>>>> of 0 - q->num_buffers-1.
>>>>>
>>>>> Perhaps add a comment to that effect, but otherwise you can drop the checks.
>>>>>
>>>>>> +
>>>>>> +    if (vb->num_planes != 1) {
>>>>>>             ret = -EBUSY;
>>>>>>             goto err_reqbufs;
>>>>>>         }
>>>>>> @@ -2688,12 +2791,17 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>>>>          * Get kernel address of each buffer.
>>>>>>          */
>>>>>>         for (i = 0; i < q->num_buffers; i++) {
>>>>>> -        fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
>>>>>> +        vb = vb2_get_buffer(q, i);
>>>>>> +
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        fileio->bufs[i].vaddr = vb2_plane_vaddr(vb, 0);
>>>>>>             if (fileio->bufs[i].vaddr == NULL) {
>>>>>>                 ret = -EINVAL;
>>>>>>                 goto err_reqbufs;
>>>>>>             }
>>>>>> -        fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
>>>>>> +        fileio->bufs[i].size = vb2_plane_size(vb, 0);
>>>>>>         }
>>>>>>           /*
>>>>>> @@ -2821,15 +2929,18 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>>>>>>               fileio->cur_index = index;
>>>>>>             buf = &fileio->bufs[index];
>>>>>> -        b = q->bufs[index];
>>>>>> +        b = vb2_get_buffer(q, index);
>>>>>> +
>>>>>> +        if (!b)
>>>>>> +            return -EINVAL;
>>>>>>               /*
>>>>>>              * Get number of bytes filled by the driver
>>>>>>              */
>>>>>>             buf->pos = 0;
>>>>>>             buf->queued = 0;
>>>>>> -        buf->size = read ? vb2_get_plane_payload(q->bufs[index], 0)
>>>>>> -                 : vb2_plane_size(q->bufs[index], 0);
>>>>>> +        buf->size = read ? vb2_get_plane_payload(b, 0)
>>>>>> +                 : vb2_plane_size(b, 0);
>>>>>>             /* Compensate for data_offset on read in the multiplanar case. */
>>>>>>             if (is_multiplanar && read &&
>>>>>>                     b->planes[0].data_offset < buf->size) {
>>>>>> @@ -2872,8 +2983,12 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>>>>>>          * Queue next buffer if required.
>>>>>>          */
>>>>>>         if (buf->pos == buf->size || (!read && fileio->write_immediately)) {
>>>>>> -        struct vb2_buffer *b = q->bufs[index];
>>>>>> +        struct vb2_buffer *b = vb2_get_buffer(q, index);
>>>>>>     +        if (!b) {
>>>>>> +            dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +            return -EINVAL;
>>>>>> +        }
>>>>>>             /*
>>>>>>              * Check if this is the last buffer to read.
>>>>>>              */
>>>>>> @@ -2899,7 +3014,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>>>>>>              */
>>>>>>             buf->pos = 0;
>>>>>>             buf->queued = 1;
>>>>>> -        buf->size = vb2_plane_size(q->bufs[index], 0);
>>>>>> +        buf->size = vb2_plane_size(b, 0);
>>>>>>             fileio->q_count += 1;
>>>>>>             /*
>>>>>>              * If we are queuing up buffers for the first time, then
>>>>>> @@ -2970,7 +3085,9 @@ static int vb2_thread(void *data)
>>>>>>              * Call vb2_dqbuf to get buffer back.
>>>>>>              */
>>>>>>             if (prequeue) {
>>>>>> -            vb = q->bufs[index++];
>>>>>> +            vb = vb2_get_buffer(q, index++);
>>>>>> +            if (!vb)
>>>>>> +                continue;
>>>>>>                 prequeue--;
>>>>>>             } else {
>>>>>>                 call_void_qop(q, wait_finish, q);
>>>>>> @@ -2979,7 +3096,7 @@ static int vb2_thread(void *data)
>>>>>>                 call_void_qop(q, wait_prepare, q);
>>>>>>                 dprintk(q, 5, "file io: vb2_dqbuf result: %d\n", ret);
>>>>>>                 if (!ret)
>>>>>> -                vb = q->bufs[index];
>>>>>> +                vb = vb2_get_buffer(q, index);
>>>>>>             }
>>>>>>             if (ret || threadio->stop)
>>>>>>                 break;
>>>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>>> index c7a54d82a55e..724135d41f7f 100644
>>>>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>>> @@ -383,8 +383,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>>>>>>             return -EINVAL;
>>>>>>         }
>>>>>>     -    if (q->bufs[b->index] == NULL) {
>>>>>> -        /* Should never happen */
>>>>>> +    if (!vb2_get_buffer(q, b->index)) {
>>>>>>             dprintk(q, 1, "%s: buffer is NULL\n", opname);
>>>>> How about:
>>>>>
>>>>>              dprintk(q, 1, "%s: buffer %u was deleted\n", opname, b->index);
>>>>>
>>>>> although perhaps that change is more appropriate in patch 09/10?
>>>>>
>>>>> Regardless, once it is possible to delete buffers, then this message should be
>>>>> adjusted accordingly.
>>>>>
>>>>>>             return -EINVAL;
>>>>>>         }
>>>>>> @@ -394,7 +393,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>>>>>>             return -EINVAL;
>>>>>>         }
>>>>>>     -    vb = q->bufs[b->index];
>>>>>> +    vb = vb2_get_buffer(q, b->index);
>>>>> This can be moved up to the 'if (!vb2_get_buffer(q, b->index)) {' check above.
>>>>> That avoids calling vb2_get_buffer twice.
>>>>>
>>>>>>         vbuf = to_vb2_v4l2_buffer(vb);
>>>>>>         ret = __verify_planes_array(vb, b);
>>>>>>         if (ret)
>>>>>> @@ -628,11 +627,18 @@ static const struct vb2_buf_ops v4l2_buf_ops = {
>>>>>>     struct vb2_buffer *vb2_find_buffer(struct vb2_queue *q, u64 timestamp)
>>>>>>     {
>>>>>>         unsigned int i;
>>>>>> +    struct vb2_buffer *vb2;
>>>>>>     -    for (i = 0; i < q->num_buffers; i++)
>>>>>> -        if (q->bufs[i]->copied_timestamp &&
>>>>>> -            q->bufs[i]->timestamp == timestamp)
>>>>>> -            return vb2_get_buffer(q, i);
>>>>> Perhaps add a comment here that this loop doesn't scale if there
>>>>> is a really large number of buffers and something more efficient
>>>>> will have to be found in that case.
>>>>>
>>>>>> +    for (i = 0; i < q->num_buffers; i++) {
>>>>>> +        vb2 = vb2_get_buffer(q, i);
>>>>>> +
>>>>>> +        if (!vb2)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        if (vb2->copied_timestamp &&
>>>>>> +            vb2->timestamp == timestamp)
>>>>>> +            return vb2;
>>>>>> +    }
>>>>>>         return NULL;
>>>>>>     }
>>>>>>     EXPORT_SYMBOL_GPL(vb2_find_buffer);
>>>>>> @@ -664,7 +670,13 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
>>>>>>             dprintk(q, 1, "buffer index out of range\n");
>>>>>>             return -EINVAL;
>>>>>>         }
>>>>>> -    vb = q->bufs[b->index];
>>>>>> +    vb = vb2_get_buffer(q, b->index);
>>>>>> +
>>>>>> +    if (!vb) {
>>>>>> +        dprintk(q, 1, "can't find the requested buffer\n");
>>>>>> +        return -EINVAL;
>>>>>> +    }
>>>>>> +
>>>>>>         ret = __verify_planes_array(vb, b);
>>>>>>         if (!ret)
>>>>>>             vb2_core_querybuf(q, b->index, b);
>>>>>> diff --git a/drivers/media/platform/amphion/vpu_dbg.c b/drivers/media/platform/amphion/vpu_dbg.c
>>>>>> index 982c2c777484..a462d6fe4ea9 100644
>>>>>> --- a/drivers/media/platform/amphion/vpu_dbg.c
>>>>>> +++ b/drivers/media/platform/amphion/vpu_dbg.c
>>>>>> @@ -140,11 +140,18 @@ static int vpu_dbg_instance(struct seq_file *s, void *data)
>>>>>>           vq = v4l2_m2m_get_src_vq(inst->fh.m2m_ctx);
>>>>>>         for (i = 0; i < vq->num_buffers; i++) {
>>>>>> -        struct vb2_buffer *vb = vq->bufs[i];
>>>>>> -        struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
>>>>>> +        struct vb2_buffer *vb;
>>>>>> +        struct vb2_v4l2_buffer *vbuf;
>>>>>> +
>>>>>> +        vb = vb2_get_buffer(vq, i);
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>>               if (vb->state == VB2_BUF_STATE_DEQUEUED)
>>>>>>                 continue;
>>>>>> +
>>>>>> +        vbuf = to_vb2_v4l2_buffer(vb);
>>>>>> +
>>>>>>             num = scnprintf(str, sizeof(str),
>>>>>>                     "output [%2d] state = %10s, %8s\n",
>>>>>>                     i, vb2_stat_name[vb->state],
>>>>>> @@ -155,11 +162,18 @@ static int vpu_dbg_instance(struct seq_file *s, void *data)
>>>>>>           vq = v4l2_m2m_get_dst_vq(inst->fh.m2m_ctx);
>>>>>>         for (i = 0; i < vq->num_buffers; i++) {
>>>>>> -        struct vb2_buffer *vb = vq->bufs[i];
>>>>>> -        struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
>>>>>> +        struct vb2_buffer *vb;
>>>>>> +        struct vb2_v4l2_buffer *vbuf;
>>>>>> +
>>>>>> +        vb = vb2_get_buffer(vq, i);
>>>>>> +        if (!vb)
>>>>>> +            continue;
>>>>>>               if (vb->state == VB2_BUF_STATE_DEQUEUED)
>>>>>>                 continue;
>>>>>> +
>>>>>> +        vbuf = to_vb2_v4l2_buffer(vb);
>>>>>> +
>>>>>>             num = scnprintf(str, sizeof(str),
>>>>>>                     "capture[%2d] state = %10s, %8s\n",
>>>>>>                     i, vb2_stat_name[vb->state],
>>>>> This can be a separate patch, right? It doesn't depend on any core changes.
>>>>>
>>>>> And this can also be applied before this patch.
>>>> Hans, I would like to clarify this comment (and the following Ditto).
>>>> Are you against use vb2_get_buffer() outside core ?
>>>> or testing vb2_get_buffer() result ?
>>>> The goal of this patch was to remove all access like vq->bufs[i] and to make
>>>> sure that vb buffer are always valid.
>>> Sorry for the confusion. I meant that AFAICS each of these driver changes can be
>>> done in the separate patch and that those separate patches can be applied before
>>> this patch. I.e., they are independent.
>>>
>>> I always prefer specific driver changes to be done as separate patches rather
>>> than one patch modifying a lot of drivers in one go. That is not always possible,
>>> of course, but in this case I think it is fine, unless I missed something.
>> All changes in the drivers use vb2_get_buffer() which is introduced in this patch
>> so I can't do them before.
>> If you want I can make a patch per driver but after this patch.
> ??? vb2_get_buffer() has been defined in include/media/videobuf2-core.h for a long
> time (2019 to be precise).

Yes I have made a mistake, sorry for the noise.

>
> Regards,
>
> 	Hans
>
>> Regards,
>> Benjamin
>>
>>> Regards,
>>>
>>>      Hans
>>>
>>>> Regards,
>>>> Benjamin
>>>>
>>>>>> diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
>>>>>> index 621038aab116..62910a1b8a98 100644
>>>>>> --- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
>>>>>> +++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
>>>>>> @@ -603,7 +603,11 @@ static int mtk_jpeg_qbuf(struct file *file, void *priv, struct v4l2_buffer *buf)
>>>>>>             return -EINVAL;
>>>>>>         }
>>>>>>     -    vb = vq->bufs[buf->index];
>>>>>> +    vb = vb2_get_buffer(vq, buf->index);
>>>>>> +    if (!vb) {
>>>>>> +        dev_err(ctx->jpeg->dev, "buffer not found\n");
>>>>>> +        return -EINVAL;
>>>>>> +    }
>>>>>>         jpeg_src_buf = mtk_jpeg_vb2_to_srcbuf(vb);
>>>>>>         jpeg_src_buf->bs_size = buf->m.planes[0].bytesused;
>>>>>>     
>>>>> Ditto.
>>>>>
>>>>>> diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
>>>>>> index e393e3e668f8..3d2ae0e1b5b6 100644
>>>>>> --- a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
>>>>>> +++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
>>>>>> @@ -1696,7 +1696,7 @@ static int vdec_vp9_slice_setup_core_buffer(struct vdec_vp9_slice_instance *inst
>>>>>>           /* update internal buffer's width/height */
>>>>>>         for (i = 0; i < vq->num_buffers; i++) {
>>>>>> -        if (vb == vq->bufs[i]) {
>>>>>> +        if (vb == vb2_get_buffer(vq, i)) {
>>>>>>                 instance->dpb[i].width = w;
>>>>>>                 instance->dpb[i].height = h;
>>>>>>                 break;
>>>>> Ditto.
>>>>>
>>>>>> diff --git a/drivers/media/platform/st/sti/hva/hva-v4l2.c b/drivers/media/platform/st/sti/hva/hva-v4l2.c
>>>>>> index 3a848ca32a0e..326be09bdb55 100644
>>>>>> --- a/drivers/media/platform/st/sti/hva/hva-v4l2.c
>>>>>> +++ b/drivers/media/platform/st/sti/hva/hva-v4l2.c
>>>>>> @@ -577,6 +577,10 @@ static int hva_qbuf(struct file *file, void *priv, struct v4l2_buffer *buf)
>>>>>>             }
>>>>>>               vb2_buf = vb2_get_buffer(vq, buf->index);
>>>>>> +        if (!vb2_buf) {
>>>>>> +            dev_dbg(dev, "%s buffer index %d not found\n", ctx->name, buf->index);
>>>>>> +            return -EINVAL;
>>>>>> +        }
>>>>>>             stream = to_hva_stream(to_vb2_v4l2_buffer(vb2_buf));
>>>>>>             stream->bytesused = buf->bytesused;
>>>>>>         }
>>>>> Ditto.
>>>>>
>>>>>> diff --git a/drivers/media/test-drivers/visl/visl-dec.c b/drivers/media/test-drivers/visl/visl-dec.c
>>>>>> index 318d675e5668..ba20ea998d19 100644
>>>>>> --- a/drivers/media/test-drivers/visl/visl-dec.c
>>>>>> +++ b/drivers/media/test-drivers/visl/visl-dec.c
>>>>>> @@ -290,13 +290,20 @@ static void visl_tpg_fill(struct visl_ctx *ctx, struct visl_run *run)
>>>>>>         for (i = 0; i < out_q->num_buffers; i++) {
>>>>>>             char entry[] = "index: %u, state: %s, request_fd: %d, ";
>>>>>>             u32 old_len = len;
>>>>>> -        char *q_status = visl_get_vb2_state(out_q->bufs[i]->state);
>>>>>> +        struct vb2_buffer *vb2;
>>>>>> +        char *q_status;
>>>>>> +
>>>>>> +        vb2 = vb2_get_buffer(out_q, i);
>>>>>> +        if (!vb2)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        q_status = visl_get_vb2_state(vb2->state);
>>>>>>               len += scnprintf(&buf[len], TPG_STR_BUF_SZ - len,
>>>>>>                      entry, i, q_status,
>>>>>> -                 to_vb2_v4l2_buffer(out_q->bufs[i])->request_fd);
>>>>>> +                 to_vb2_v4l2_buffer(vb2)->request_fd);
>>>>>>     -        len += visl_fill_bytesused(to_vb2_v4l2_buffer(out_q->bufs[i]),
>>>>>> +        len += visl_fill_bytesused(to_vb2_v4l2_buffer(vb2),
>>>>>>                            &buf[len],
>>>>>>                            TPG_STR_BUF_SZ - len);
>>>>>>     @@ -342,13 +349,20 @@ static void visl_tpg_fill(struct visl_ctx *ctx, struct visl_run *run)
>>>>>>         len = 0;
>>>>>>         for (i = 0; i < cap_q->num_buffers; i++) {
>>>>>>             u32 old_len = len;
>>>>>> -        char *q_status = visl_get_vb2_state(cap_q->bufs[i]->state);
>>>>>> +        struct vb2_buffer *vb2;
>>>>>> +        char *q_status;
>>>>>> +
>>>>>> +        vb2 = vb2_get_buffer(cap_q, i);
>>>>>> +        if (!vb2)
>>>>>> +            continue;
>>>>>> +
>>>>>> +        q_status = visl_get_vb2_state(vb2->state);
>>>>>>               len += scnprintf(&buf[len], TPG_STR_BUF_SZ - len,
>>>>>>                      "index: %u, status: %s, timestamp: %llu, is_held: %d",
>>>>>> -                 cap_q->bufs[i]->index, q_status,
>>>>>> -                 cap_q->bufs[i]->timestamp,
>>>>>> -                 to_vb2_v4l2_buffer(cap_q->bufs[i])->is_held);
>>>>>> +                 vb2->index, q_status,
>>>>>> +                 vb2->timestamp,
>>>>>> +                 to_vb2_v4l2_buffer(vb2)->is_held);
>>>>>>               tpg_gen_text(&ctx->tpg, basep, line++ * line_height, 16, &buf[old_len]);
>>>>>>             frame_dprintk(ctx->dev, run->dst->sequence, "%s", &buf[old_len]);
>>>>> Ditto.
>>>>>
>>>>>> diff --git a/drivers/staging/media/atomisp/pci/atomisp_ioctl.c b/drivers/staging/media/atomisp/pci/atomisp_ioctl.c
>>>>>> index d2174156573a..4b65c69fa60d 100644
>>>>>> --- a/drivers/staging/media/atomisp/pci/atomisp_ioctl.c
>>>>>> +++ b/drivers/staging/media/atomisp/pci/atomisp_ioctl.c
>>>>>> @@ -1061,7 +1061,7 @@ static int atomisp_dqbuf_wrapper(struct file *file, void *fh, struct v4l2_buffer
>>>>>>         if (ret)
>>>>>>             return ret;
>>>>>>     -    vb = pipe->vb_queue.bufs[buf->index];
>>>>>> +    vb = vb2_get_buffer(&pipe->vb_queue, buf->index);
>>>>>>         frame = vb_to_frame(vb);
>>>>>>           buf->reserved = asd->frame_status[buf->index];
>>>>> Ditto.
>>>>>
>>>>> Background: I think it is really useful to merge a lot of the groundwork early
>>>>> on, where possible. It simplifies the remainder of the patch series.
>>>>>
>>>>> Regards,
>>>>>
>>>>>       Hans
>>>>>
>