Commit a92fb3fe authored by Andrew Morton's avatar Andrew Morton Committed by Dave Jones

[PATCH] pgd_index/pmd_index/pte_index commentary

Patch from Dave Hansen <haveblue@us.ibm.com>

Adds some commentary to these newly-introduced macros.
parent d6ff057c
......@@ -231,18 +231,41 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
#define pmd_large(pmd) \
((pmd_val(pmd) & (_PAGE_PSE|_PAGE_PRESENT)) == (_PAGE_PSE|_PAGE_PRESENT))
/* to find an entry in a page-table-directory. */
/*
* the pgd page can be thought of an array like this: pgd_t[PTRS_PER_PGD]
*
* this macro returns the index of the entry in the pgd page which would
* control the given virtual address
*/
#define pgd_index(address) (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))
/*
* pgd_offset() returns a (pgd_t *)
* pgd_index() is used get the offset into the pgd page's array of pgd_t's;
*/
#define pgd_offset(mm, address) ((mm)->pgd+pgd_index(address))
/* to find an entry in a kernel page-table-directory */
/*
* a shortcut which implies the use of the kernel's pgd, instead
* of a process's
*/
#define pgd_offset_k(address) pgd_offset(&init_mm, address)
/*
* the pmd page can be thought of an array like this: pmd_t[PTRS_PER_PMD]
*
* this macro returns the index of the entry in the pmd page which would
* control the given virtual address
*/
#define pmd_index(address) \
(((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))
/* Find an entry in the third-level page table.. */
/*
* the pte page can be thought of an array like this: pte_t[PTRS_PER_PTE]
*
* this macro returns the index of the entry in the pte page which would
* control the given virtual address
*/
#define pte_index(address) \
(((address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
#define pte_offset_kernel(dir, address) \
......
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