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Message-ID: <20230519101916.dt25jofubidrasd2@chromium.org>
Date: Fri, 19 May 2023 10:19:16 +0000
From: Tomasz Figa <tfiga@...omium.org>
To: Benjamin Gaignard <benjamin.gaignard@...labora.com>
Cc: m.szyprowski@...sung.com, mchehab@...nel.org, ming.qian@....com,
shijie.qin@....com, eagle.zhou@....com, bin.liu@...iatek.com,
matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
tiffany.lin@...iatek.com, andrew-ct.chen@...iatek.com,
yunfei.dong@...iatek.com, stanimir.k.varbanov@...il.com,
quic_vgarodia@...cinc.com, agross@...nel.org, andersson@...nel.org,
konrad.dybcio@...aro.org, ezequiel@...guardiasur.com.ar,
p.zabel@...gutronix.de, daniel.almeida@...labora.com,
hverkuil-cisco@...all.nl, laurent.pinchart@...asonboard.com,
jernel@...nel.org, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
linux-rockchip@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v2 3/8] media: videobuf2: Add a module param to limit vb2
queue buffer storage
On Tue, Mar 21, 2023 at 11:28:50AM +0100, Benjamin Gaignard wrote:
> Add module parameter "max_vb_buffer_per_queue" to be able to limit
> the number of vb2 buffers store in queue.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> ---
> drivers/media/common/videobuf2/videobuf2-core.c | 15 +++------------
> include/media/videobuf2-core.h | 11 +++++++++--
> 2 files changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index ae9d72f4d181..f4da917ccf3f 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -34,6 +34,8 @@
> static int debug;
> module_param(debug, int, 0644);
>
> +module_param(max_vb_buffer_per_queue, ulong, 0644);
> +
> #define dprintk(q, level, fmt, arg...) \
> do { \
> if (debug >= level) \
> @@ -412,10 +414,6 @@ 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 */
> - num_buffers = min_t(unsigned int, num_buffers,
> - VB2_MAX_FRAME - q->num_buffers);
> -
We should keep the validation here, just using the new module parameter
instead of VB2_MAX_FRAME. Otherwise we let the userspace pass
UINT_MAX to REQBUFS and have the array below exhaust the system memory.
> for (buffer = 0; buffer < num_buffers; ++buffer) {
> /* Allocate vb2 buffer structures */
> vb = kzalloc(q->buf_struct_size, GFP_KERNEL);
> @@ -801,9 +799,7 @@ 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);
Similar concern here.
> memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
> /*
> * Set this now to ensure that drivers see the correct q->memory value
> @@ -919,11 +915,6 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> bool no_previous_buffers = !q->num_buffers;
> int ret;
>
> - if (q->num_buffers == VB2_MAX_FRAME) {
> - dprintk(q, 1, "maximum number of buffers already allocated\n");
> - return -ENOBUFS;
> - }
> -
Ditto.
> if (no_previous_buffers) {
> if (q->waiting_in_dqbuf && *count) {
> dprintk(q, 1, "another dup()ped fd is waiting for a buffer\n");
> @@ -948,7 +939,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> return -EINVAL;
> }
>
> - num_buffers = min(*count, VB2_MAX_FRAME - q->num_buffers);
> + num_buffers = *count;
Ditto.
>
> if (requested_planes && requested_sizes) {
> num_planes = requested_planes;
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 397dbf6e61e1..b8b34a993e04 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -12,6 +12,7 @@
> #ifndef _MEDIA_VIDEOBUF2_CORE_H
> #define _MEDIA_VIDEOBUF2_CORE_H
>
> +#include <linux/minmax.h>
> #include <linux/mm_types.h>
> #include <linux/mutex.h>
> #include <linux/poll.h>
> @@ -48,6 +49,8 @@ struct vb2_fileio_data;
> struct vb2_threadio_data;
> struct vb2_buffer;
>
> +static size_t max_vb_buffer_per_queue = 1024;
> +
> /**
> * struct vb2_mem_ops - memory handling/memory allocator operations.
> * @alloc: allocate video memory and, optionally, allocator private data,
> @@ -1268,12 +1271,16 @@ static inline bool vb2_queue_add_buffer(struct vb2_queue *q, struct vb2_buffer *
>
> if (vb->index >= q->max_num_bufs) {
> struct vb2_buffer **tmp;
> + int cnt = min(max_vb_buffer_per_queue, q->max_num_bufs * 2);
Should cnt also be size_t to match max_vb_buffer_per_queue?
This could also overflow given q->max_num_bufs big enough, so maybe it
would just be better to rewrite to?
size_t cnt = (q->max_num_bufs > max_vb_buffer_per_queue / 2) ?
max_vb_buffer_per_queue : q->max_num_bufs * 2;
Or we could just switch to XArray and it would solve this for us. :)
Best regards,
Tomasz
> +
> + if (cnt >= q->max_num_bufs)
> + goto realloc_failed;
>
> - tmp = krealloc_array(q->bufs, q->max_num_bufs * 2, sizeof(*q->bufs), GFP_KERNEL);
> + tmp = krealloc_array(q->bufs, cnt, sizeof(*q->bufs), GFP_KERNEL);
> if (!tmp)
> goto realloc_failed;
>
> - q->max_num_bufs *= 2;
> + q->max_num_bufs = cnt;
> q->bufs = tmp;
> }
>
> --
> 2.34.1
>
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