Hi folks,
Are there any more comments? Will this be accepted?
On Fri, Jun 30, 2017 at 4:58 PM, Olga Kornievskaia <kolga@xxxxxxxxxx> wrote:
> Allow copy_file_range to copy between different superblocks but only
> of the same file system types.
>
> 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 | 7 +++++++
> fs/read_write.c | 13 ++++++-------
> 2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
> index f42b906..0c243f6 100644
> --- a/Documentation/filesystems/vfs.txt
> +++ b/Documentation/filesystems/vfs.txt
> @@ -845,6 +845,8 @@ struct file_operations {
> #ifndef CONFIG_MMU
> unsigned (*mmap_capabilities)(struct file *);
> #endif
> + ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
> + loff_t, size_t, unsigned int);
> };
>
> Again, all methods are called without any locks being held, unless
> @@ -913,6 +915,11 @@ otherwise noted.
>
> fallocate: called by the VFS to preallocate blocks or punch a hole.
>
> + 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.
> +
> +
> Note that the file operations are implemented by the specific
> filesystem in which the inode resides. When opening a device node
> (character or block special) most filesystems will call special
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 47c1d44..f981d49 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1589,10 +1589,6 @@ 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;
>
> @@ -1602,7 +1598,8 @@ 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) {
> @@ -1611,10 +1608,12 @@ 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;
> }
>
> --
> 1.8.3.1
>
> --
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