Re: [PATCH v2] copy_file_range: limit size if in compat mode

[Chunsheng Luo <luochunsheng@xxxxxxxx>]

On Wed, Aug 13, 2025 at 5:11 PM Miklos Szeredi wrote:
> @@ -1624,8 +1629,7 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
>  	 * to splicing from input file, while file_start_write() is held on
>  	 * the output file on a different sb.
>  	 */
> -	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> -			       min_t(size_t, len, MAX_RW_COUNT), 0);
> +	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out, len, 0);
>  done:
>  	if (ret > 0) {
>  		fsnotify_access(file_in);

There is no problem with submission, but I have a doubt in the call chain:
`do_splice_direct -> do_splice_direct_actor:`
static ssize_t do_splice_direct_actor(struct file *in, loff_t *ppos,
				      struct file *out, loff_t *opos,
				      size_t len, unsigned int flags,
				      splice_direct_actor *actor)
{
	struct splice_desc sd = {
		.len		= len,  //unsigned int len
		.total_len	= len, 
		...
	};
	
The len member in the struct splice_desc is of type unsigned int. 
The assignment here may cause truncation, but in reality, this len
won't be used. Can we directly delete it? 
Otherwise, it's very confusing here.

Thanks
Chunsheng Luo