On Fri, 2018-10-26 at 16:10 -0400, Olga Kornievskaia wrote:
> From: Olga Kornievskaia <kolga@xxxxxxxxxx>
>
> This patch makes it the responsibility of individual filesystems to
> allow or deny cross device copies. Both NFS and CIFS have operations
> for cross-server copies, and later patches will implement this feature.
>
> Note that as of this patch, the copy_file_range() function might be passed
> superblocks from different filesystem types. -EXDEV should be returned
> if cross device copies aren't supported, causing the VFS to fall back
> on using do_splice_direct().
>
> Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
> ---
> Documentation/filesystems/porting | 7 +++++++
> fs/cifs/cifsfs.c | 3 +++
> fs/nfs/nfs4file.c | 3 +++
> fs/overlayfs/file.c | 3 +++
> fs/read_write.c | 9 +++------
> 5 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
> index 7b7b845..897e1e7 100644
> --- a/Documentation/filesystems/porting
> +++ b/Documentation/filesystems/porting
> @@ -622,3 +622,10 @@ in your dentry operations instead.
> alloc_file_clone(file, flags, ops) does not affect any caller's references.
> On success you get a new struct file sharing the mount/dentry with the
> original, on failure - ERR_PTR().
> +--
> +[mandatory]
> + ->copy_file_range() may now be passed files which belong to two
> + different superblocks of the same file system type or which belong
> + to two different filesystems types all together. As before, the
> + destination's copy_file_range() is the function which is called.
> + If it cannot copy ranges from the source, it should return -EXDEV.
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 7065426..f2d7f4f 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -1114,6 +1114,9 @@ static ssize_t cifs_copy_file_range(struct file *src_file, loff_t off,
> unsigned int xid = get_xid();
> ssize_t rc;
>
> + if (src_file->f_inode->i_sb != dst_file->f_inode->i_sb)
> + return -EXDEV;
> +
> rc = cifs_file_copychunk_range(xid, src_file, off, dst_file, destoff,
> len, flags);
> free_xid(xid);
> diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
> index 4288a6e..09df688 100644
> --- a/fs/nfs/nfs4file.c
> +++ b/fs/nfs/nfs4file.c
> @@ -135,6 +135,9 @@ static ssize_t nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
> {
> ssize_t ret;
>
> + if (file_in->f_inode->i_sb != file_out->f_inode->i_sb)
> + return -EXDEV;
> +
> if (file_inode(file_in) == file_inode(file_out))
> return -EINVAL;
> retry:
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index aeaefd2..5282853 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -483,6 +483,9 @@ static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out,
> size_t len, unsigned int flags)
> {
> + if (file_in->f_inode->i_sb != file_out->f_inode->i_sb)
> + return -EXDEV;
> +
> return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
> OVL_COPY);
> }
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 39b4a21..fb4ffca 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1575,10 +1575,6 @@ 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;
>
> @@ -1588,7 +1584,8 @@ 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) {
> @@ -1600,7 +1597,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> if (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;
> }
>
Yes, this is the right way to do this sort of change, IMO. Push the
checks down into the fs' so they can be relaxed on a case-by-case basis.
Modulo dchinner's comments, this looks fine.
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
