vfs: vfs_clone_file_prep_inodes should return EINVAL for a clone from beyond EOF

vfs_clone_file_prep_inodes cannot return 0 if it is asked to remap from
a zero byte file because that's what btrfs does.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/read_write.c

@@ -1740,10 +1740,7 @@ int vfs_clone_file_prep_inodes(struct inode *inode_in, loff_t pos_in,
 	if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
 		return -EINVAL;
 
-	/* Are we going all the way to the end? */
 	isize = i_size_read(inode_in);
-	if (isize == 0)
-		return 0;
 
 	/* Zero length dedupe exits immediately; reflink goes to EOF. */
 	if (*len == 0) {