Subject: Re: mmotm 2014-04-22-15-20 uploaded (uml 32- and 64-bit defconfigs)

From: Nishanth Aravamudan <[email-masked]>
Date: Wed, 23 Apr 2014 16:31:24 -0700

On 24.04.2014 [08:10:19 +1000], Stephen Rothwell wrote:
> Hi all,
> 
> On Wed, 23 Apr 2014 11:24:42 -0700 Andrew Morton <[email-masked]> wrote:
> >
> > I'll try moving hugepages_supported() into the #ifdef
> > CONFIG_HUGETLB_PAGE section.
> > 
> > --- a/include/linux/hugetlb.h~hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported-fix-fix
> > +++ a/include/linux/hugetlb.h
> > @@ -412,6 +412,16 @@ static inline spinlock_t *huge_pte_lockp
> >  	return &mm->page_table_lock;
> >  }
> >  
> > +static inline bool hugepages_supported(void)
> > +{
> > +	/*
> > +	 * Some platform decide whether they support huge pages at boot
> > +	 * time. On these, such as powerpc, HPAGE_SHIFT is set to 0 when
> > +	 * there is no such support
> > +	 */
> > +	return HPAGE_SHIFT != 0;
> > +}
> > +
> >  #else	/* CONFIG_HUGETLB_PAGE */
> >  struct hstate {};
> >  #define alloc_huge_page_node(h, nid) NULL
> > @@ -460,14 +470,4 @@ static inline spinlock_t *huge_pte_lock(
> >  	return ptl;
> >  }
> >  
> > -static inline bool hugepages_supported(void)
> > -{
> > -	/*
> > -	 * Some platform decide whether they support huge pages at boot
> > -	 * time. On these, such as powerpc, HPAGE_SHIFT is set to 0 when
> > -	 * there is no such support
> > -	 */
> > -	return HPAGE_SHIFT != 0;
> > -}
> > -
> >  #endif /* _LINUX_HUGETLB_H */
> 
> Clearly, noone reads my emails :-(
> 
> This is exactly what I reported and the fix I applied to yesterday's
> linux-next ...

Actually, I think (based upon the context) that your fix is slightly
different. Your fix puts hugepages_supported() under CONFIG_HUGETLBFS.
Andrew's puts it under CONFIG_HUGETLB_PAGE. I think they are effectively
tied together as options go, but it semantically makes more sense with
CONFIG_HUGETLB_PAGE.

Thanks,
Nish

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