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Subject: Re: [PATCH -V2] powerpc: thp: Fix crash on mremap
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Date: Thu, 02 Jan 2014 23:29:46 +1100
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Cc: aarcange@redhat.com, linuxppc-dev@lists.ozlabs.org, paulus@samba.org,
 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, linux-mm@kvack.org
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On Thu, 2014-01-02 at 16:22 +0530, Aneesh Kumar K.V wrote:
> > Just use config option directly:
> >
> >       if (new_ptl != old_ptl ||
> >               IS_ENABLED(CONFIG_ARCH_THP_MOVE_PMD_ALWAYS_WITHDRAW))
> 
> 
> I didn't like that. I found the earlier one easier for reading.
> If you and others strongly feel about this, I can redo the patch.
> Please let me know

Yes, use IS_ENABLED, no need to have two indirections of #define's

Another option is to have

	if (pmd_move_must_withdraw(new,old)) {
	}

With in a generic header:

#ifndef pmd_move_must_withdraw
static inline bool pmd_move_must_withdraw(spinlock_t *new_ptl, ...)
{
	return new_ptl != old_ptl;
}
#endif

And in powerpc:

static inline bool pmd_move_must_withdraw(spinlock_t *new_ptl, ...)
{
	return true;
}
#define pmd_move_must_withdraw pmd_move_must_withdraw

Cheers,
Ben.