Re: [PATCH v2 1/6] dma-buf: Rename and expose debugfs symbols

["Christian König" <christian.koenig@amd.com>]

On 5/5/25 00:41, T.J. Mercier wrote:
> Expose the debugfs list and mutex so they are usable for the creation of
> a BPF iterator for dmabufs without the need for CONFIG_DEBUG_FS. Rename
> the symbols so it's clear debugfs is not required, and that the list
> contains dmabufs and not some other type.
> 
> Signed-off-by: T.J. Mercier <tjmercier@google.com>

Reviewed-by: Christian König <christian.koenig@amd.com>

> ---
> v2: Make the DMA buffer list independent of CONFIG_DEBUG_FS per Christian König
>  drivers/dma-buf/dma-buf.c | 40 +++++++++++++++------------------------
>  include/linux/dma-buf.h   |  6 ++++--
>  2 files changed, 19 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 5baa83b85515..7260bdd77c75 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -35,35 +35,25 @@
>  
>  static inline int is_dma_buf_file(struct file *);
>  
> -#if IS_ENABLED(CONFIG_DEBUG_FS)
> -static DEFINE_MUTEX(debugfs_list_mutex);
> -static LIST_HEAD(debugfs_list);
> +DEFINE_MUTEX(dmabuf_list_mutex);
> +LIST_HEAD(dmabuf_list);
>  
> -static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
> +static void __dma_buf_list_add(struct dma_buf *dmabuf)
>  {
> -	mutex_lock(&debugfs_list_mutex);
> -	list_add(&dmabuf->list_node, &debugfs_list);
> -	mutex_unlock(&debugfs_list_mutex);
> +	mutex_lock(&dmabuf_list_mutex);
> +	list_add(&dmabuf->list_node, &dmabuf_list);
> +	mutex_unlock(&dmabuf_list_mutex);
>  }
>  
> -static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf)
> +static void __dma_buf_list_del(struct dma_buf *dmabuf)
>  {
>  	if (!dmabuf)
>  		return;
>  
> -	mutex_lock(&debugfs_list_mutex);
> +	mutex_lock(&dmabuf_list_mutex);
>  	list_del(&dmabuf->list_node);
> -	mutex_unlock(&debugfs_list_mutex);
> +	mutex_unlock(&dmabuf_list_mutex);
>  }
> -#else
> -static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
> -{
> -}
> -
> -static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf)
> -{
> -}
> -#endif
>  
>  static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
>  {
> @@ -115,7 +105,7 @@ static int dma_buf_file_release(struct inode *inode, struct file *file)
>  	if (!is_dma_buf_file(file))
>  		return -EINVAL;
>  
> -	__dma_buf_debugfs_list_del(file->private_data);
> +	__dma_buf_list_del(file->private_data);
>  
>  	return 0;
>  }
> @@ -689,7 +679,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
>  	file->f_path.dentry->d_fsdata = dmabuf;
>  	dmabuf->file = file;
>  
> -	__dma_buf_debugfs_list_add(dmabuf);
> +	__dma_buf_list_add(dmabuf);
>  
>  	return dmabuf;
>  
> @@ -1630,7 +1620,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  	size_t size = 0;
>  	int ret;
>  
> -	ret = mutex_lock_interruptible(&debugfs_list_mutex);
> +	ret = mutex_lock_interruptible(&dmabuf_list_mutex);
>  
>  	if (ret)
>  		return ret;
> @@ -1639,7 +1629,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  	seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\tname\n",
>  		   "size", "flags", "mode", "count", "ino");
>  
> -	list_for_each_entry(buf_obj, &debugfs_list, list_node) {
> +	list_for_each_entry(buf_obj, &dmabuf_list, list_node) {
>  
>  		ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
>  		if (ret)
> @@ -1676,11 +1666,11 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  
>  	seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
>  
> -	mutex_unlock(&debugfs_list_mutex);
> +	mutex_unlock(&dmabuf_list_mutex);
>  	return 0;
>  
>  error_unlock:
> -	mutex_unlock(&debugfs_list_mutex);
> +	mutex_unlock(&dmabuf_list_mutex);
>  	return ret;
>  }
>  
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 36216d28d8bd..ebcd208272bf 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -18,6 +18,7 @@
>  #include <linux/err.h>
>  #include <linux/scatterlist.h>
>  #include <linux/list.h>
> +#include <linux/mutex.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/fs.h>
>  #include <linux/dma-fence.h>
> @@ -370,10 +371,8 @@ struct dma_buf {
>  	 */
>  	struct module *owner;
>  
> -#if IS_ENABLED(CONFIG_DEBUG_FS)
>  	/** @list_node: node for dma_buf accounting and debugging. */
>  	struct list_head list_node;
> -#endif
>  
>  	/** @priv: exporter specific private data for this buffer object. */
>  	void *priv;
> @@ -556,6 +555,9 @@ struct dma_buf_export_info {
>  	struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
>  					 .owner = THIS_MODULE }
>  
> +extern struct list_head dmabuf_list;
> +extern struct mutex dmabuf_list_mutex;
> +
>  /**
>   * get_dma_buf - convenience wrapper for get_file.
>   * @dmabuf:	[in]	pointer to dma_buf