Messages in this thread Patch in this message | | | Date | Mon, 21 Nov 2011 14:23:36 -0800 | From | David Daney <> | Subject | Re: [patch] hugetlb: remove dummy definitions of HPAGE_MASK and HPAGE_SIZE |
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Linus,
It may not have been evident when you committed this (commit a5c86e986f0b2fe779f13cf53ce6e9f467b03950), but there was considerable discussion around this patch.
Andrew had taken into his tree a couple of patches to make the definitions that David Rientjes is removing safer:
http://marc.info/?l=linux-kernel&m=132156712623915&w=2 http://marc.info/?l=linux-kernel&m=132156712523914&w=2
David objected, but Andrew wasn't convinced, see all the replies to this patch but especially:
http://marc.info/?l=linux-kernel&m=132157428626522&w=2
On 11/17/2011 03:22 PM, David Rientjes wrote: > Dummy, non-zero definitions for HPAGE_MASK and HPAGE_SIZE were added in > 51c6f666fceb ("mm: ZAP_BLOCK causes redundant work") to avoid a divide > by zero in generic kernel code. > > That code has since been removed, but probably should never have been > added in the first place: we don't want HPAGE_SIZE to act like PAGE_SIZE > for code that is working with hugepages, for example, when the dependency > on CONFIG_HUGETLB_PAGE has not been fulfilled. > > Because hugepage size can differ from architecture to architecture, each > is required to have their own definitions for both HPAGE_MASK and > HPAGE_SIZE. This is always done in arch/*/include/asm/page.h. > > So, just remove the dummy and dangerous definitions since they are no > longer needed and reveals the correct dependencies. Tested on > architectures using the definitions with allyesconfig: x86 (even with > thp), hppa, mips, powerpc, s390, sh3, sh4, sparc, and sparc64, and > with defconfig on ia64. >
This whole comment strikes me as somewhat dishonest, as at the time David Rientjes wrote it, he knew that there were dependencies on these symbols in the linux-next tree.
Now we can add these: +#define HPAGE_SHIFT ({ BUG(); 0; }) +#define HPAGE_SIZE ({ BUG(); 0; }) +#define HPAGE_MASK ({ BUG(); 0; })
To the different architecture header files instead of having them in the common include/linux/hugetlb.h
If this is the way Linus wants it, I can live with that. But it was a little surprising to see that this was merged when there were strong arguments against it.
David Daney
> Cc: Robin Holt<holt@sgi.com> > Cc: David Daney<david.daney@cavium.com> > Signed-off-by: David Rientjes<rientjes@google.com> > --- > include/linux/hugetlb.h | 5 ----- > 1 files changed, 0 insertions(+), 5 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -110,11 +110,6 @@ static inline void copy_huge_page(struct page *dst, struct page *src) > > #define hugetlb_change_protection(vma, address, end, newprot) > > -#ifndef HPAGE_MASK > -#define HPAGE_MASK PAGE_MASK /* Keep the compiler happy */ > -#define HPAGE_SIZE PAGE_SIZE > -#endif > - > #endif /* !CONFIG_HUGETLB_PAGE */ > > #define HUGETLB_ANON_FILE "anon_hugepage" >
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