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SubjectRe: atari partitioning problem?
On Mon, May 13, 2002 at 19:25:17 -0500, Kai Germaschewski wrote:
> 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.

Oops! You're right, thanks for pointing that out. :)

Ken
--
Kenneth Merry
ken@kdm.org
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