proc_file_read() question

[Martin Wilck]

Hi,

the "hack" below in proc_file_read() fs/proc/generic.c (2.4.5)
irritates me:

If I do use "start" for a pointer into a memory area
allocated in read_proc, will it be always guaranteed
that (start > page)?

If no, this will IMO lead to spuriously wrong output.
If yes, I'd like to understand why.

Regards & thanks,
Martin

		/* This is a hack to allow mangling of file pos independent
 		 * of actual bytes read.  Simply place the data at page,
 		 * return the bytes, and set `start' to the desired offset
 		 * as an unsigned int. - [e-mail]
		 */
 		n -= copy_to_user(buf, start < page ? page : start, n);
		if (n == 0) {
			if (retval == 0)
				retval = -EFAULT;
			break;
		}

		*ppos += start < page ? (long)start : n; /* Move down the file */

-- 
Martin Wilck     <[e-mail]>
FSC EP PS DS1, Paderborn      Tel. [phone]