NFS: replace cross device check in copy_file_range

Add a check to disallow cross file systems copy offload, both
files are expected to be of NFS4.2+ type.

Reviewed-by: Jeff Layton <[email protected]>
Reviewed-by: Matthew Wilcox <[email protected]>
Signed-off-by: Olga Kornievskaia <[email protected]>

Author: olgakorn1

fs/nfs/nfs4file.c

@@ -141,7 +141,7 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 	bool sync = false;
 
 	/* Only offload copy if superblock is the same */
-	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
+	if (file_in->f_op != &nfs4_file_operations)
 		return -EXDEV;
 	if (!nfs_server_capable(file_inode(file_out), NFS_CAP_COPY))
 		return -EOPNOTSUPP;