nfs42: add NFS_IOC_CLONE_RANGE ioctl

It follows btrfs BTRFS_IOC_CLONE_RANGE lead on ioctl number and
arguments.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4file.c

@@ -288,14 +288,28 @@ out_drop_write:
 	mnt_drop_write_file(dst_file);
 	return ret;
 }
+
+static long nfs42_ioctl_clone_range(struct file *dst_file, void __user *argp)
+{
+	struct nfs_ioctl_clone_range_args args;
+
+	if (copy_from_user(&args, argp, sizeof(args)))
+		return -EFAULT;
+
+	return nfs42_ioctl_clone(dst_file, args.src_fd, args.src_off, args.dst_off, args.count);
+}
 #endif /* CONFIG_NFS_V4_2 */
 
 long nfs4_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
+	void __user *argp = (void __user *)arg;
+
 	switch (cmd) {
 #ifdef CONFIG_NFS_V4_2
 	case NFS_IOC_CLONE:
 		return nfs42_ioctl_clone(file, arg, 0, 0, 0);
+	case NFS_IOC_CLONE_RANGE:
+		return nfs42_ioctl_clone_range(file, argp);
 #endif
 	}
 

include/uapi/linux/nfs.h

@@ -33,7 +33,14 @@
 
 /* NFS ioctls */
 /* Let's follow btrfs lead on CLONE to avoid messing userspace */
-#define NFS_IOC_CLONE	_IOW(0x94, 9, int)
+#define NFS_IOC_CLONE		_IOW(0x94, 9, int)
+#define NFS_IOC_CLONE_RANGE	_IOW(0x94, 13, int)
+
+struct nfs_ioctl_clone_range_args {
+	__s64 src_fd;
+	__u64 src_off, count;
+	__u64 dst_off;
+};
 
 /*
  * NFS stats. The good thing with these values is that NFSv3 errors are