linux-kernel - Re: [PATCH 3/3] mm/memory_hotplug: fix unpaired mem_hotplug

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Date:   Tue, 7 Jul 2020 15:10:22 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Jia He <justin.he@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        Chuhong Yuan <hslester96@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>, Kaly Xin <Kaly.Xin@....com>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH 3/3] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done

On Mon, Jul 6, 2020 at 12:50 AM David Hildenbrand <david@...hat.com> wrote:
>
> On 06.07.20 03:19, Jia He wrote:
> > When check_memblock_offlined_cb() returns failed rc(e.g. the memblock is
> > online at that time), mem_hotplug_begin/done is unpaired in such case.
> >
> > Therefore a warning:
> >  Call Trace:
> >   percpu_up_write+0x33/0x40
> >   try_remove_memory+0x66/0x120
> >   ? _cond_resched+0x19/0x30
> >   remove_memory+0x2b/0x40
> >   dev_dax_kmem_remove+0x36/0x72 [kmem]
> >   device_release_driver_internal+0xf0/0x1c0
> >   device_release_driver+0x12/0x20
> >   bus_remove_device+0xe1/0x150
> >   device_del+0x17b/0x3e0
> >   unregister_dev_dax+0x29/0x60
> >   devm_action_release+0x15/0x20
> >   release_nodes+0x19a/0x1e0
> >   devres_release_all+0x3f/0x50
> >   device_release_driver_internal+0x100/0x1c0
> >   driver_detach+0x4c/0x8f
> >   bus_remove_driver+0x5c/0xd0
> >   driver_unregister+0x31/0x50
> >   dax_pmem_exit+0x10/0xfe0 [dax_pmem]
> >
> > This fixes it by moving mem_hotplug_done ahead of "done"
> >
> > Signed-off-by: Jia He <justin.he@....com>
> > ---
> >  mm/memory_hotplug.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index e1e290577b45..86b36714342b 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1769,8 +1769,8 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
> >
> >       try_offline_node(nid);
> >
> > -done:
> >       mem_hotplug_done();
> > +done:
> >       return rc;
> >  }
> >
> >
>
> Just drop the "done" label, use "return rc;" directly instead of the
> goto, and "return 0;" at the end.
>
> Also, please add
>
> Fixes: f1037ec0cc8a ("mm/memory_hotplug: fix remove_memory() lockdep splat")
>
> and
>
> Cc: stable@...r.kernel.org # v5.6+
>
> Thanks!

Yes, thanks, you can also add:

Acked-by: Dan Williams <dan.j.williams@...el.com>