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SubjectRe: Still ext2-corruption in test8-pre5 (incl. OOPS)


On Wed, 6 Sep 2000, Tim Waugh wrote:
> On Tue, Sep 05, 2000 at 07:14:02PM -0700, Linus Torvalds wrote:
>
> > How about this patch?
>
> Got this oops.

This one I cannot explain.

It's a bh that is NULL, but it's a new case completely. It looks like you
have a 1kB blocksize, no? It furthermore looks like the page only had two
buffers on it, and accessing the fourth one blows up (accessing the third
one gets NULL, which is why it only blows up on the fourth one).

But it _has_ to have four buffers on it. Two buffers just aren't enough to
cover a 4kB page.

Uh.

DUH!

I found the bug.

It shouldn't be "bh->b_next". That's just the next buffer on the hash
chain.

It should be "bh->b_this_page".

Just change block_truncate_page() to use b_this_page instead of b_next.

The "good news" is that me testing this would neve rhave found it, because
all my filesystems are 4kB blocks, so the "next bh" case never triggers at
all.

Thanks, and THIS time it really is fixed. I mean, how many times can we
get it wrong? At some point, we just have to run out of really bad ideas..

Linus

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