Messages in this thread | | | Date | Tue, 25 Jun 2013 09:46:24 -0700 | From | Dave Hansen <> | Subject | Re: [PATCHv4 27/39] x86-64, mm: proper alignment mappings with hugepages |
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On 06/25/2013 07:56 AM, Kirill A. Shutemov wrote: > Dave Hansen wrote: >> On 05/11/2013 06:23 PM, Kirill A. Shutemov wrote: >>> +static inline unsigned long mapping_align_mask(struct address_space *mapping) >>> +{ >>> + if (mapping_can_have_hugepages(mapping)) >>> + return PAGE_MASK & ~HPAGE_MASK; >>> + return get_align_mask(); >>> +} >> >> get_align_mask() appears to be a bit more complicated to me than just a >> plain old mask. Are you sure you don't need to pick up any of its >> behavior for the mapping_can_have_hugepages() case? > > get_align_mask() never returns more strict mask then we do in > mapping_can_have_hugepages() case. > > I can modify it this way: > > unsigned long mask = get_align_mask(); > > if (mapping_can_have_hugepages(mapping)) > mask &= PAGE_MASK & ~HPAGE_MASK; > return mask; > > But it looks more confusing for me. What do you think?
Personally, I find that a *LOT* more clear. The &= pretty much spells out what you said in your explanation: get_align_mask()'s mask can only be made more strict when we encounter a huge page.
The relationship between the two masks is not apparent at all in your original code. This is all nitpicking though, I just wanted to make sure you'd considered if you were accidentally changing behavior.
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