linux-kernel - Re: [PATCH] dma-buf: Add DmaBufTotal counter in meminfo

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Message-ID: <8287166c-6899-e723-ac2c-fa49f5a69a5a@amd.com>
Date:   Fri, 16 Apr 2021 13:20:27 +0200
From:   Christian König <christian.koenig@....com>
To:     Peter Enderborg <peter.enderborg@...y.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Muchun Song <songmuchun@...edance.com>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...e.com>, NeilBrown <neilb@...e.de>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Mike Rapoport <rppt@...nel.org>, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH] dma-buf: Add DmaBufTotal counter in meminfo

Am 16.04.21 um 11:37 schrieb Peter Enderborg:
> This adds a total used dma-buf memory. Details
> can be found in debugfs, however it is not for everyone
> and not always available.

Well you are kind of missing the intention here.

I mean knowing this is certainly useful in some case, but you need to 
describe which cases that are.

Christian.

>
> Signed-off-by: Peter Enderborg <peter.enderborg@...y.com>
> ---
>   drivers/dma-buf/dma-buf.c | 12 ++++++++++++
>   fs/proc/meminfo.c         |  2 ++
>   include/linux/dma-buf.h   |  1 +
>   3 files changed, 15 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index f264b70c383e..9f88171b394c 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_size;
>   
>   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_size);
>   	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_size);
>   
>   	return dmabuf;
>   
> @@ -1346,6 +1349,15 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
>   }
>   EXPORT_SYMBOL_GPL(dma_buf_vunmap);
>   
> +/**
> + * dma_buf_get_size - Return the used nr pages by dma-buf
> + */
> +long dma_buf_get_size(void)
> +{
> +	return atomic_long_read(&dma_buf_size) >> PAGE_SHIFT;
> +}
> +EXPORT_SYMBOL_GPL(dma_buf_get_size);
> +
>   #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..3c1a82b51a6f 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"
>   
> @@ -145,6 +146,7 @@ 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
> +	show_val_kb(m, "DmaBufTotal:    ", dma_buf_get_size());
>   
>   	hugetlb_report_meminfo(m);
>   
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index efdc56b9d95f..f6481315a377 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_get_size(void);
>   #endif /* __DMA_BUF_H__ */