Date: Thu, 30 May 1996 22:19:02 +1000 From: Bruce Evans <bde@zeta.org.au> To: freebsd-scsi@freebsd.org, wilko@yedi.iaf.nl Subject: Re: removing 32 kbyte limit from dump Message-ID: <199605301219.WAA19690@godzilla.zeta.org.au>
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>But I'm not really satisfied by this. I'd rather see that the st.c
>driver returns EINVAL or something like that when an attempt is made
>to write an impossible block size (and of course dump should act
>accordingly when it receives the error value).
96K is not impossible. It just gets mutilated to 64K+32K by physio(),
and the error isn't detected because both 64K and 32K are possible.
physio() needs to have a do-not-split flag.
Similar problems probably affect cd and worm devices. An i/o of
100 * 2352 byte blocks would be mutilated at 64K boundaries. This
can be fixed using the current physio() interface: don't use rawread()/
rawwrite(), and provided a minphys() function that returns
(MAXPHYS / 2352) * 2352 (it must be <= MAXPHYS because physio()
uses min(MAXPHYS, minphys()).
>--- 167,177 ----
> case 'b': /* blocks per tape write */
> ntrec = numarg('b', "number of blocks per write",
> 1L, 1000L, &argc, &argv);
>! /* XXX physio() is currently unable > 64 kByte I/Os */
>! /* so lets tell the user now and not wait for him/her
>! /* to see the console message */
>! if ( ntrec > 64 ) {
>! msg("Please choose a blocksize <= 64 \n");
> exit(X_ABORT);
64 should be MAXPHYS/1024.
Bruce
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