Re: [PATCH -V2] powerpc: thp: Fix crash on mremap

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

> 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

This is better i guess. It is also in-line with rest of transparent
hugepage functions. I will do this.

-aneesh