Re: [PATCH 2/2] mm: hugetlb: support gigantic surplus pages

[Huang Shijie <shijie.huang@arm.com>]

On Tue, Nov 08, 2016 at 08:27:42PM +0100, Gerald Schaefer wrote:
> On Tue, 8 Nov 2016 17:17:28 +0800
> Huang Shijie <shijie.huang@arm.com> wrote:
> 
> > > I will look at the lockdep issue.
> > I tested the new patch (will be sent out later) on the arm64 platform,
> > and I did not meet the lockdep issue when I enabled the lockdep.
> > The following is my config:
> > 
> > 	CONFIG_LOCKD=y
> > 	CONFIG_LOCKD_V4=y
> > 	CONFIG_LOCKUP_DETECTOR=y
> >         # CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC is not set
> > 	CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE=0
> > 	CONFIG_DEBUG_SPINLOCK=y
> > 	CONFIG_DEBUG_LOCK_ALLOC=y
> > 	CONFIG_PROVE_LOCKING=y
> > 	CONFIG_LOCKDEP=y
> > 	CONFIG_LOCK_STAT=y
> > 	CONFIG_DEBUG_LOCKDEP=y
> > 	CONFIG_DEBUG_LOCKING_API_SELFTESTS=y
> > 	
> > So do I miss something? 
> 
> Those options should be OK. Meanwhile I looked into this a little more,
> and the problematic line/lock is spin_lock_irqsave(&z->lock, flags) at
> the top of alloc_gigantic_page(). From the lockdep trace we see that
> it is triggered by an mmap(), and then hugetlb_acct_memory() ->
> __alloc_huge_page() -> alloc_gigantic_page().
> 
> However, in between those functions (inside gather_surplus_pages())
> a NUMA_NO_NODE node id comes into play. And this finally results in
> alloc_gigantic_page() being called with NUMA_NO_NODE as nid (which is
> -1), and NODE_DATA(nid)->node_zones will then reach into Nirvana.
Thanks for pointing this.
I sent out the new patch just now. Could you please try it again?
I added a NUMA_NO_NODE check in the alloc_gigantic_page();

thanks
Huang Shijie

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