RE: [patch] fix ia64 hugetlb_free_pgd_range

[Chen, Kenneth W]

David Gibson wrote on Thursday, February 23, 2006 8:06 PM
> But I don't see how not transforming them sometimes can be correct.
> Suppose 'floor' is only a little way below 'addr' - addr will be
> shifted down, but floor won't, so floor may now be above addr, which
> will cause weird results.
> 
> Afaict the *only* thing floor and ceiling are used for is bounds
> checking the address range we're examining.  How can that ever be
> right if one address has been scaled down, but the other hasn't.

The scale down isn't exactly on every address bits.  Top 3 bits of
virtual address are preserved.

#define htlbpage_to_page(x)    (((unsigned long) REGION_NUMBER(x) << 61)
                                 | (REGION_OFFSET(x) >>
(HPAGE_SHIFT-PAGE_SHIFT)))

So scaled address for a hugetlb address will never be below unscaled
normal page address.  That is adjusted addr will never below unchanged
floor.

- Ken
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