Re: [Linaro-mm-sig] [PATCH v3 2/2] dmabuf: Add dmabuf inode number to /proc/*/fdinfo

On Fri, Feb 5, 2021 at 2:56 AM Christian König christian.koenig@amd.com wrote:

Am 05.02.21 um 03:23 schrieb Kalesh Singh:

...

If a FD refers to a DMA buffer add the DMA buffer inode number to /proc/<pid>/fdinfo/<FD> and /proc/<pid>/task/<tid>/fdindo/<FD>.

The dmabuf inode number allows userspace to uniquely identify the buffer and avoids a dependency on /proc/<pid>/fd/* when accounting per-process DMA buffer sizes.

BTW: Why do we make this DMA-buf specific? Couldn't we always print the inode number for all fds?

Good point. We can make this a common field instead of DMA buf specific. I will update in the next version.

Thanks, Kalesh

Regards, Christian.

...

Signed-off-by: Kalesh Singh kaleshsingh@google.com

Changes in v3:

• Add documentation in proc.rst

Changes in v2:

• Update patch description

Documentation/filesystems/proc.rst | 17 +++++++++++++++++ drivers/dma-buf/dma-buf.c | 1 + 2 files changed, 18 insertions(+)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 2fa69f710e2a..fdd38676f57f 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -2031,6 +2031,23 @@ details]. 'it_value' is remaining time until the timer expiration. with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' still exhibits timer's remaining time.

+DMA Buffer files +~~~~~~~~~~~~~~~~

+::

• pos:    0
  

• flags:  04002
  

• mnt_id: 9
  

• dmabuf_inode_no: 63107
  

• size:   32768
  

• count:  2
  

• exp_name:  system-heap
  

+where 'dmabuf_inode_no' is the unique inode number of the DMA buffer file. +'size' is the size of the DMA buffer in bytes. 'count' is the file count of +the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter.

• 3.9 /proc/<pid>/map_files - Information about memory mapped files

  This directory contains symbolic links which represent memory mapped files

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 9ad6397aaa97..d869099ede83 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -414,6 +414,7 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) { struct dma_buf *dmabuf = file->private_data;

• seq_printf(m, "dmabuf_inode_no:\t%lu\n", file_inode(file)->i_ino);
  seq_printf(m, "size:\t%zu\n", dmabuf->size);
  /* Don't count the temporary reference taken inside procfs seq_show */
  seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);