Re: [External] [PATCH v4] dma-buf: Add DmaBufTotal counter in meminfo

[Muchun Song <songmuchun@bytedance.com>]

On Sat, Apr 17, 2021 at 6:41 PM Peter Enderborg
<peter.enderborg@sony.com> wrote:
>
> This adds a total used dma-buf memory. Details
> can be found in debugfs, however it is not for everyone
> and not always available. dma-buf are indirect allocated by
> userspace. So with this value we can monitor and detect
> userspace applications that have problems.
>
> Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> ---
>  drivers/dma-buf/dma-buf.c | 13 +++++++++++++
>  fs/proc/meminfo.c         |  5 ++++-
>  include/linux/dma-buf.h   |  1 +
>  3 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index f264b70c383e..197e5c45dd26 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -37,6 +37,7 @@ struct dma_buf_list {
>  };
>
>  static struct dma_buf_list db_list;
> +static atomic_long_t dma_buf_global_allocated;
>
>  static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
>  {
> @@ -79,6 +80,7 @@ static void dma_buf_release(struct dentry *dentry)
>         if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
>                 dma_resv_fini(dmabuf->resv);
>
> +       atomic_long_sub(dmabuf->size, &dma_buf_global_allocated);
>         module_put(dmabuf->owner);
>         kfree(dmabuf->name);
>         kfree(dmabuf);
> @@ -586,6 +588,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
>         mutex_lock(&db_list.lock);
>         list_add(&dmabuf->list_node, &db_list.head);
>         mutex_unlock(&db_list.lock);
> +       atomic_long_add(dmabuf->size, &dma_buf_global_allocated);
>
>         return dmabuf;
>
> @@ -1346,6 +1349,16 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
>  }
>  EXPORT_SYMBOL_GPL(dma_buf_vunmap);
>
> +/**
> + * dma_buf_allocated_pages - Return the used nr of pages
> + * allocated for dma-buf
> + */
> +long dma_buf_allocated_pages(void)
> +{
> +       return atomic_long_read(&dma_buf_global_allocated) >> PAGE_SHIFT;
> +}
> +EXPORT_SYMBOL_GPL(dma_buf_allocated_pages);

dma_buf_allocated_pages is only called from fs/proc/meminfo.c.
I am confused why it should be exported. If it won't be called
from the driver module, we should not export it.

Thanks.

> +
>  #ifdef CONFIG_DEBUG_FS
>  static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  {
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 6fa761c9cc78..ccc7c40c8db7 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -16,6 +16,7 @@
>  #ifdef CONFIG_CMA
>  #include <linux/cma.h>
>  #endif
> +#include <linux/dma-buf.h>
>  #include <asm/page.h>
>  #include "internal.h"
>
> @@ -145,7 +146,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>         show_val_kb(m, "CmaFree:        ",
>                     global_zone_page_state(NR_FREE_CMA_PAGES));
>  #endif
> -
> +#ifdef CONFIG_DMA_SHARED_BUFFER
> +       show_val_kb(m, "DmaBufTotal:    ", dma_buf_allocated_pages());
> +#endif
>         hugetlb_report_meminfo(m);
>
>         arch_report_meminfo(m);
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index efdc56b9d95f..5b05816bd2cd 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -507,4 +507,5 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
>                  unsigned long);
>  int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
>  void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
> +long dma_buf_allocated_pages(void);
>  #endif /* __DMA_BUF_H__ */
> --
> 2.17.1
>