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SubjectRe: [PATCH v6 08/71] Maple Tree: Add new data structure
Date


* Vasily Gorbik <gor@linux.ibm.com> [220301 17:51]:
> On Tue, Mar 01, 2022 at 08:39:44PM +0000, Liam Howlett wrote:
> > * Vasily Gorbik <gor@linux.ibm.com> [220228 21:01]:
> > > This condition is not present in mas_dead_leaves() where we potentially
> > > iterate over all 16 slots, simply checking that we have a "valid" node pointer
> > > with:
> > >
> > > entry & ~MAPLE_NODE_MASK != 0
> >
> > I have fixed this and another issue that Hugh pointed out [1]. I have
> > been working on an s390 VM since you reported your issue and have been
> > getting strange behaviour and have been able to detect the bug reported
> > by Hugh with the config KASAN option. With the fix I described above
> > and fixing the do_mas_align_munmap() splitting order I broken in my
> > linked list removal, I am now able to boot my s390 VM and log in with
> > KASAN, VM debug, maple tree debug, rbtree debug, debug page flags, and
> > Poison pages after freeing all set in the config I use. I've pushed the
> > fix to a tag on my branch [2] and I'd appreciate it if you could test it
> > on your side.
>
> Great, I gave it a spin and it looks much better now! I'll go run some stress
> tests.
>
> BTW, since you've made efforts to isolate mapple tests in userspace I
> wonder how much sense it would make to use libfuzzer to give API some good
> coverage-guided exercise.
>
> I've written a minimal libfuzzer test (just a hack) for the "Normal API" and got
> couple of flavours of crashes. Just rebased onto your latest branch state
> and still get them. Please have a look if those are valid findings.


Thanks! Yes, the first one is certainly a valid bug. I was able to
reproduce it and fix the issue in my tree. I'll have a look and see
what else it throws out.

Cheers,
Liam
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