Re: [PATCH v7 00/70] Introducing the Maple Tree

Yu Zhao
2022-04-25T18:06:38Z

On Wed, Apr 20, 2022 at 7:43 AM Liam Howlett <liam.howlett@oracle.com> wrote:
>
> * Yu Zhao <yuzhao@google.com> [220419 19:23]:
> > On Tue, Apr 19, 2022 at 5:18 PM Liam Howlett <liam.howlett@oracle.com> wrote:
> > >
> > > * Yu Zhao <yuzhao@google.com> [220419 17:59]:
> > > > On Tue, Apr 19, 2022 at 9:51 AM Liam Howlett <liam.howlett@oracle.com> wrote:
> > > > >
> > > > > * Yu Zhao <yuzhao@google.com> [220416 15:30]:
> > > > > > On Sat, Apr 16, 2022 at 9:19 AM Liam Howlett <liam.howlett@oracle.com> wrote:
> > > > > > >
> > > > > >
> > > > > > <snipped>
> > > > > >
> > > > > > > How did you hit this issue? Just on boot?
> > > > > >
> > > > > > I was hoping this is known to you or you have something I can verify for you.
> > > > >
> > > > >
> > > > > Thanks, yes. I believe that both crashes are the same root cause. The
> > > > > cause is that I was not cleaning up after the kmem bulk allocation
> > > > > failure on my side. Please test with this patch.
> > > >
> > > > Thanks. I applied this patch and hit a LOCKDEP and then a BUG_ON:
> > > >
> > > > lib/maple_tree.c:847 suspicious rcu_dereference_protected() usage!
> > > > Call Trace:
> > > > <TASK>
> > > > dump_stack_lvl+0x6c/0x9a
> > > > dump_stack+0x10/0x12
> > > > lockdep_rcu_suspicious+0x12c/0x140
> > > > __mt_destroy+0x96/0xd0
> > > > exit_mmap+0x2a0/0x360
> > > > __mmput+0x34/0x100
> > > > mmput+0x2f/0x40
> > > > free_bprm+0x64/0xe0
> > > > kernel_execve+0x129/0x330
> > > > call_usermodehelper_exec_async+0xd8/0x130
> > > > ? proc_cap_handler+0x210/0x210
> > > > ret_from_fork+0x1f/0x30
> > > > </TASK>
> > >
> > > Thanks - I'm not sure how this got through, but this should fix it.
> > >
> > > This should be added to 4236a642ad185 to avoid the LOCKDEP issue.
> > >
> > > --- a/mm/mmap.c
> > > +++ b/mm/mmap.c
> > > @@ -3163,9 +3163,9 @@ void exit_mmap(struct mm_struct *mm)
> > >
> > > BUG_ON(count != mm->map_count);
> > >
> > > - mmap_write_unlock(mm);
> > > trace_exit_mmap(mm);
> > > __mt_destroy(&mm->mm_mt);
> > > + mmap_write_unlock(mm);
> > > vm_unacct_memory(nr_accounted);
> > > }
> >
> > Will try this.
>
>
> Andrew,
>
> Please add this fix to the commit 4236a642ad185 "mm: start tracking VMAs
> with maple tree"
>
> I've attached the patch for your convenience.

Hi Liam,

I assume you are still looking at the BUG_ON problem. I'll restart my
testing once you have something for me to try.

Thanks.