proc_file_read() question

From: Martin Wilck (Martin.Wilck@fujitsu-siemens.com)
Date: Mon Jun 25 2001 - 14:46:27 EST

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. - Paul.Russell@rustcorp.com.au
                 */
                 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     <Martin.Wilck@fujitsu-siemens.com>
FSC EP PS DS1, Paderborn      Tel. +49 5251 8 15113

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This archive was generated by hypermail 2b29 : Sat Jun 30 2001 - 21:00:12 EST