xarray: Replace exceptional entries
Introduce xarray value entries and tagged pointers to replace radix tree exceptional entries. This is a slight change in encoding to allow the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a value entry). It is also a change in emphasis; exceptional entries are intimidating and different. As the comment explains, you can choose to store values or pointers in the xarray and they are both first-class citizens. Signed-off-by: Matthew Wilcox <willy@infradead.org> Reviewed-by: Josef Bacik <jbacik@fb.com>
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@@ -313,9 +313,7 @@ static inline void __ptep_set_access_flags(struct vm_area_struct *vma,
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#define MAX_SWAPFILES_CHECK() do { \
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BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS); \
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} while (0)
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/*
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* on pte we don't need handle RADIX_TREE_EXCEPTIONAL_SHIFT;
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*/
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#define SWP_TYPE_BITS 5
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#define __swp_type(x) (((x).val >> _PAGE_BIT_SWAP_TYPE) \
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& ((1UL << SWP_TYPE_BITS) - 1))
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