Re: [PATCH 2/2] dma-buf: Add debugfs support

Laurent Pinchart
2013-03-27T00:07:42Z

Hi Sumit,

Thanks for the patch.

On Monday 25 March 2013 16:50:46 Sumit Semwal wrote:
> Add debugfs support to make it easier to print debug information
> about the dma-buf buffers.
>
> Cc: Dave Airlie <airlied@redhat.com>
> [minor fixes on init and warning fix]
> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
> ---
> changes since v1:
> - fixes on init and warnings as reported and corrected by Dave Airlie.
> - add locking while walking attachment list - reported by Daniel Vetter.
>
> drivers/base/dma-buf.c | 162 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/dma-buf.h | 5 +-
> 2 files changed, 166 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index d89102a..7d867ed 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -27,9 +27,18 @@
> #include <linux/dma-buf.h>
> #include <linux/anon_inodes.h>
> #include <linux/export.h>
> +#include <linux/debugfs.h>
> +#include <linux/seq_file.h>
>
> static inline int is_dma_buf_file(struct file *);
>
> +struct dma_buf_list {
> + struct list_head head;
> + struct mutex lock;
> +};
> +
> +static struct dma_buf_list db_list;
> +
> static int dma_buf_release(struct inode *inode, struct file *file)
> {
> struct dma_buf *dmabuf;
> @@ -42,6 +51,11 @@ static int dma_buf_release(struct inode *inode, struct
> file *file) BUG_ON(dmabuf->vmapping_counter);
>
> dmabuf->ops->release(dmabuf);
> +
> + mutex_lock(&db_list.lock);
> + list_del(&dmabuf->list_node);
> + mutex_unlock(&db_list.lock);
> +
> kfree(dmabuf);
> return 0;
> }
> @@ -125,6 +139,10 @@ struct dma_buf *dma_buf_export_named(void *priv, const
> struct dma_buf_ops *ops, mutex_init(&dmabuf->lock);
> INIT_LIST_HEAD(&dmabuf->attachments);
>
> + mutex_lock(&db_list.lock);
> + list_add(&dmabuf->list_node, &db_list.head);
> + mutex_unlock(&db_list.lock);
> +
> return dmabuf;
> }
> EXPORT_SYMBOL_GPL(dma_buf_export_named);
> @@ -551,3 +569,147 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, void
> *vaddr) mutex_unlock(&dmabuf->lock);
> }
> EXPORT_SYMBOL_GPL(dma_buf_vunmap);
> +
> +static int dma_buf_init_debugfs(void);
> +static void dma_buf_uninit_debugfs(void);
> +
> +static int __init dma_buf_init(void)
> +{
> + mutex_init(&db_list.lock);
> + INIT_LIST_HEAD(&db_list.head);
> + dma_buf_init_debugfs();
> + return 0;
> +}
> +
> +subsys_initcall(dma_buf_init);
> +
> +static void __exit dma_buf_deinit(void)

This function is never called.

> +{
> + dma_buf_uninit_debugfs();
> +}

If you moved those two functions at the end of the file you could get rid of
the forward declarations above.

> +
> +#ifdef CONFIG_DEBUG_FS
> +static int dma_buf_describe(struct seq_file *s)
> +{
> + int ret;
> + struct dma_buf *buf_obj;
> + struct dma_buf_attachment *attach_obj;
> + int count = 0, attach_count;
> + size_t size = 0;
> +
> + ret = mutex_lock_interruptible(&db_list.lock);
> +
> + if (ret)
> + return ret;
> +
> + seq_printf(s, "\nDma-buf Objects:\n");
> + seq_printf(s, "\texp_name\tsize\tflags\tmode\tcount\n");
> +
> + list_for_each_entry(buf_obj, &db_list.head, list_node) {
> + ret = mutex_lock_interruptible(&buf_obj->lock);
> +
> + if (ret) {
> + seq_printf(s,
> + "\tERROR locking buffer object: skipping\n");
> + goto skip_buffer;
> + }
> +
> + seq_printf(s, "\t");
> +
> + seq_printf(s, "\t%s\t%08zu\t%08x\t%08x\t%08d\n",
> + buf_obj->exp_name, buf_obj->size,
> + buf_obj->file->f_flags, buf_obj->file->f_mode,
> + buf_obj->file->f_count.counter);
> +
> + seq_printf(s, "\t\tAttached Devices:\n");
> + attach_count = 0;
> +
> + list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
> + seq_printf(s, "\t\t");
> +
> + seq_printf(s, "%s\n", attach_obj->dev->init_name);
> + attach_count++;
> + }
> +
> + seq_printf(s, "\n\t\tTotal %d devices attached\n",
> + attach_count);
> +
> + count++;
> + size += buf_obj->size;
> +skip_buffer:
> + mutex_unlock(&buf_obj->lock);
> + }
> +
> + seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
> +
> + mutex_unlock(&db_list.lock);
> + return 0;
> +}
> +
> +static int dma_buf_show(struct seq_file *s, void *unused)
> +{
> + void (*func)(struct seq_file *) = s->private;
> + func(s);
> + return 0;
> +}
> +
> +static int dma_buf_debug_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, dma_buf_show, inode->i_private);
> +}
> +
> +static const struct file_operations dma_buf_debug_fops = {
> + .open = dma_buf_debug_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +static struct dentry *dma_buf_debugfs_dir;
> +
> +static int dma_buf_init_debugfs(void)
> +{
> + int err = 0;
> + dma_buf_debugfs_dir = debugfs_create_dir("dma_buf", NULL);
> + if (IS_ERR(dma_buf_debugfs_dir)) {
> + err = PTR_ERR(dma_buf_debugfs_dir);
> + dma_buf_debugfs_dir = NULL;
> + return err;
> + }
> +
> + err = dma_buf_debugfs_create_file("bufinfo", dma_buf_describe);
> +
> + if (err)
> + pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
> +
> + return err;
> +}
> +
> +static void dma_buf_uninit_debugfs(void)
> +{
> + if (dma_buf_debugfs_dir)
> + debugfs_remove_recursive(dma_buf_debugfs_dir);
> +}
> +
> +int dma_buf_debugfs_create_file(const char *name,
> + int (*write)(struct seq_file *))
> +{
> + struct dentry *d;
> +
> + d = debugfs_create_file(name, S_IRUGO, dma_buf_debugfs_dir,
> + write, &dma_buf_debug_fops);
> +
> + if (IS_ERR(d))
> + return PTR_ERR(d);
> +
> + return 0;
> +}
> +#else
> +static inline int dma_buf_init_debugfs(void)
> +{
> + return 0;
> +}
> +static inline void dma_buf_uninit_debugfs(void)
> +{
> +}
> +#endif
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 6f55c04..dfac5ed 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -113,6 +113,7 @@ struct dma_buf_ops {
> * @attachments: list of dma_buf_attachment that denotes all devices
> attached. * @ops: dma_buf_ops associated with this buffer object.
> * @exp_name: name of the exporter; useful for debugging.
> + * @list_node: node for dma_buf accounting and debugging.
> * @priv: exporter specific private data for this buffer object.
> */
> struct dma_buf {
> @@ -125,6 +126,7 @@ struct dma_buf {
> unsigned vmapping_counter;
> void *vmap_ptr;
> const char *exp_name;
> + struct list_head list_node;
> void *priv;
> };
>
> @@ -192,5 +194,6 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct
> *, unsigned long);
> void *dma_buf_vmap(struct dma_buf *);
> void dma_buf_vunmap(struct dma_buf *, void *vaddr);
> -
> +int dma_buf_debugfs_create_file(const char *name,
> + int (*write)(struct seq_file *));

This function is only called internally from the same file, could it be
declared as static ?

> #endif /* __DMA_BUF_H__ */
--
Regards,

Laurent Pinchart