Re: [RFC PATCH v2 1/1] misc: fgds: introduce GPU-File direct I/O via dma-buf

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Oct 27, 2026 at 07:03:29AM -0600, Jens Axboe wrote:
> On 10/27/26 3:08 AM, Li Wang wrote:
> > From: Mengmeng Zhao <zhaomengmeng@kylinos.cn>
> > 
> > This patch introduces a driver that allows moving data between a GPU
> > dma-buf and a regular file on NVME without staging it through the page 
> > cache. Userspace registers the GPU dma-buf with the device, then issues 
> > read and write requests via the device's ioctls. Each transfer is direct 
> > I/O: an ITER_DMABUF_MAP iterator is passed to the file's read_iter or
> > write_iter, and the filesystem's iomap path submits REQ_DMABUF bios that
> > already carry the dma addresses.
> > 
> > Signed-off-by: Mengmeng Zhao <zhaomengmeng@kylinos.cn>
> > Signed-off-by: Li Wang <liwang@kylinos.cn>
> > ---
> >  .../userspace-api/ioctl/ioctl-number.rst      |   2 +
> >  drivers/dma-buf/dma-buf-io.c                  |   3 +
> >  drivers/misc/Kconfig                          |  16 +
> >  drivers/misc/Makefile                         |   1 +
> >  drivers/misc/fgds.c                           | 506 ++++++++++++++++++
> >  fs/iomap/buffered-io.c                        |  11 +
> >  fs/iomap/direct-io.c                          |  23 +-
> >  fs/xfs/xfs_file.c                             |   4 +
> >  include/linux/iov_iter.h                      |   4 +
> >  include/uapi/linux/fgds.h                     | 124 +++++
> >  lib/iov_iter.c                                |   1 +
> >  mm/filemap.c                                  |  22 +-
> >  12 files changed, 713 insertions(+), 4 deletions(-)
> >  create mode 100644 drivers/misc/fgds.c
> >  create mode 100644 include/uapi/linux/fgds.h
> 
> What's the point of this, when you can just use io_uring to do
> the same?!

Agreed, I thought that the summary of the last round of reviews was
"this isn't needed at all".  Li, what changed from that?

thanks,

greg k-h