Re: atari partitioning problem?

[Kai Germaschewski]

On Mon, 13 May 2002, Kenneth D. Merry wrote:

> [ Al Viro CCed, since from the changelog for 2.4.11, it looks like he may
> have submitted the patch in question. ]
> 
> I was looking through the atari partitioning code (fs/partitions/atari.c)
> in 2.4.18 (from what I can see in 2.4.19-pre8, it hasn't changed) and I
> noticed something (starting at about line 144) that may be a problem:
> 
> 			for (; pi < &rs->icdpart[8] && minor < m_lim; minor++, p
> i++) {
> 				/* accept only GEM,BGM,RAW,LNX,SWP partitions */
> 				if (!((pi->flg & 1) && OK_id(pi->id)))
> 					continue;
> 				part_fmt = 2;
> 				add_gd_partition (hd, minor,
> 						  be32_to_cpu(pi->st),
> 						  be32_to_cpu(pi->siz));
> 			}
> 			printk(" >");
> 
> This code changed in 2.4.11, and was previously:
> 
>       for (; pi < &rs->icdpart[8] && minor < m_lim; minor++, pi++)
>       { 
>         /* accept only GEM,BGM,RAW,LNX,SWP partitions */
>         if (pi->flg & 1 &&
>             (memcmp (pi->id, "GEM", 3) == 0 ||
>              memcmp (pi->id, "BGM", 3) == 0 ||
>              memcmp (pi->id, "LNX", 3) == 0 ||
>              memcmp (pi->id, "SWP", 3) == 0 ||
>              memcmp (pi->id, "RAW", 3) == 0) )
>         { 
>           part_fmt = 2;
>           add_gd_partition (hd, minor, be32_to_cpu(pi->st),
>                             be32_to_cpu(pi->siz));
>         }
>       }
>       printk(" >");
> 
> Note that the test was reversed, but not fully.  You want only active
> partitions of the specified types to be added, but with the code as it is
> now, only partitions that are active and *not* of the correct type will get
> added.

No, the change is correct.

Note that the ! in the first snippet is in front of the whole expression, 
and it's pretty obvious that the reversed test for (a && b) is !(a && b).

The latter is equivalent to (!a || !b), which seems to be what you're 
thinking, but you didn't get it right and put !(a || !b) which is wrong.

--Kai