On Wed, Jun 27, 2018 at 10:46:48AM +0200, Niels de Vos wrote:
> There are several FUSE filesystems that can implement server-side copy
> or other efficient copy/duplication/clone methods. The copy_file_range()
> syscall is the standard interface that users have access to while not
> depending on external libraries that bypass FUSE.
>
> Signed-off-by: Niels de Vos <ndevos@xxxxxxxxxx>
NACK on this by myself, see reason further below.
>
> ---
> v2: return ssize_t instead of long
> ---
> fs/fuse/file.c | 65 +++++++++++++++++++++++
> fs/fuse/fuse_i.h | 3 ++
> include/uapi/linux/fuse.h | 106 ++++++++++++++++++++++----------------
> 3 files changed, 130 insertions(+), 44 deletions(-)
...
> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> index 92fa24c24c92..77330fa510f1 100644
> --- a/include/uapi/linux/fuse.h
> +++ b/include/uapi/linux/fuse.h
...
> @@ -792,4 +796,18 @@ struct fuse_lseek_out {
> uint64_t offset;
> };
>
> +struct fuse_copy_file_range_in {
> + uint64_t fh_in;
> + uint64_t off_in;
It seems that libfuse has the expectation of having access to the nodeid
when a file-descriptor is passed to userspace.
>From Marcin Sulikowski in https://github.com/libfuse/libfuse/pull/259:
> There is a caveat though – the kernel module change proposed in
> https://lkml.org/lkml/2018/6/27/114 provides only ino_in argument
> because that is passed in the request's header (args.in.h.nodeid =
> ff_in->nodeid; in fs/fuse/fuse.c in the kernel) whereas ino_out is not
> given by the kernel to the userspace implementation. Isn't this an
> oversight in the kernel module? The lack of the inode number would
> make it impossible to create high-level interface which follows the
> libfuse's convention where the high-level callbacks are given paths to
> files which are to be modified.
So, the next version of this patch will add nodeid_out to the struct.
Niels
> + uint64_t fh_out;
> + uint64_t off_out;
> + uint64_t len;
> + uint32_t flags;
> +};
> +
> +struct fuse_copy_file_range_out {
> + uint32_t size;
> + uint32_t padding;
> +};
> +
> #endif /* _LINUX_FUSE_H */
> --
> 2.17.1
>
