On Fri, 2018-10-19 at 11:29 -0400, Olga Kornievskaia wrote:
> From: Olga Kornievskaia <kolga@xxxxxxxxxx>
>
> Allow copy_file_range to copy between different superblocks but only
> of the same file system types. This feature was of interest to CIFS
> as well as NFS.
>
> This feature is needed by NFSv4.2 to perform file copy operation on
> the same server or file copy between different NFSv4.2 servers.
>
> If a file system's fileoperations copy_file_range operation prohibits
> cross-device copies, fall back to do_splice_direct. This would be
> needed for the NFS (destination) server side implementation of the
> file copy and currently for CIFS.
>
> Besides NFS, there is only 1 implementor of the copy_file_range FS
> operation -- CIFS. CIFS assumes incoming file descriptors are both
> CIFS but it will check if they are coming from different servers and
> return error code to fall back to do_splice_direct.
>
> NFS will allow for copies between different NFS servers.
>
> Adding to the vfs.txt documentation to explicitly warn about allowing
> for different superblocks of the same file type to be passed into the
> copy_file_range for the future users of copy_file_range method.
>
> Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
> ---
> Documentation/filesystems/vfs.txt | 4 +++-
> fs/read_write.c | 13 ++++++-------
> 2 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/filesystems/vfs.txt
> b/Documentation/filesystems/vfs.txt
> index a6c6a8a..5e520de 100644
> --- a/Documentation/filesystems/vfs.txt
> +++ b/Documentation/filesystems/vfs.txt
> @@ -958,7 +958,9 @@ otherwise noted.
>
> fallocate: called by the VFS to preallocate blocks or punch a
> hole.
>
> - copy_file_range: called by the copy_file_range(2) system call.
> + copy_file_range: called by copy_file_range(2) system call. This
> method
> + works on two file descriptors that might reside on
> + different superblocks of the same type of file
> system.
>
> clone_file_range: called by the ioctl(2) system call for
> FICLONERANGE and
> FICLONE commands.
> diff --git a/fs/read_write.c b/fs/read_write.c
> index c60790f..474e740 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1578,10 +1578,6 @@ ssize_t vfs_copy_file_range(struct file
> *file_in, loff_t pos_in,
> (file_out->f_flags & O_APPEND))
> return -EBADF;
>
> - /* this could be relaxed once a method supports cross-fs copies
> */
> - if (inode_in->i_sb != inode_out->i_sb)
> - return -EXDEV;
> -
> if (len == 0)
> return 0;
>
> @@ -1591,7 +1587,8 @@ ssize_t vfs_copy_file_range(struct file
> *file_in, loff_t pos_in,
> * Try cloning first, this is supported by more file systems,
> and
> * more efficient if both clone and copy are supported (e.g.
> NFS).
> */
> - if (file_in->f_op->clone_file_range) {
> + if (inode_in->i_sb == inode_out->i_sb &&
> + file_in->f_op->clone_file_range) {
> ret = file_in->f_op->clone_file_range(file_in, pos_in,
> file_out, pos_out, len);
> if (ret == 0) {
> @@ -1600,10 +1597,12 @@ ssize_t vfs_copy_file_range(struct file
> *file_in, loff_t pos_in,
> }
> }
>
> - if (file_out->f_op->copy_file_range) {
> + if (file_out->f_op->copy_file_range &&
> + (file_in->f_op->copy_file_range ==
> + file_out->f_op->copy_file_range)) {
> ret = file_out->f_op->copy_file_range(file_in, pos_in,
> file_out,
> pos_out, len,
> flags);
> - if (ret != -EOPNOTSUPP)
> + if (ret != -EOPNOTSUPP && ret != -EXDEV)
> goto done;
> }
>
Ditto. This also needs an ACK from the VFS maintainers.
Cc: Al and linux-fsdevel
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx
