Re: [bug] block subsystem related crash with latest -git

Linus Torvalds
2007-10-17T18:19:21Z

On Wed, 17 Oct 2007, Jens Axboe wrote:
> >
> > So avoiding the "sg_next()" on the last entry is pointless.
>
> Yeah, I didn't quite understand why if sg was valid, why dereferencing
> *(sg + 1)->page would crap out :/

Actually, I take that back. If 'sg' is the last entry in a *non*linked
scatter-gather list (ie we don't use the last entry as a link, we actually
use it as a real SG entry), then "sg_next(sg)" will indeed access past the
end of the whole allocated array, and will access one past the end.

And with page-alloc debugging, that *will* blow up.

So I think your change to use "sg_next()" only when you actually need a
next pointer is the correct one after all.

Linus