[EXT] [PATCH v2 3/8] media: videobuf2: Add a module param to limit vb2 queue buffer storage

[Ming Qian]

Hi Benjamin,

>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 at collabora.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);
>-
>        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);
>        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;
>-       }
>-
>        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;
>
>        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);
>+
>+               if (cnt >= q->max_num_bufs)
>+                       goto realloc_failed;
>

Is it likely that goto realloc_failed directly?
The cnt is likely equal to q->max_num_bufs * 2, and it will greater than q->max_num_bufs.
For example, the default value of q->max_num_bufs is 32, when vb->index comes to 32, cnt is 64,  it's greater than 32, then goto recalloc_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