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#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/sched.h>
#include <linux/hugetlb.h>

static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pte_t *pte;
int err = 0;

pte = pte_offset_map(pmd, addr);
for (;;) {
err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
if (err)
break;
addr += PAGE_SIZE;
if (addr == end)
break;
pte++;
}

pte_unmap(pte);
return err;
}

static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pmd_t *pmd;
unsigned long next;
int err = 0;

pmd = pmd_offset(pud, addr);
do {
again:
next = pmd_addr_end(addr, end);
if (pmd_none(*pmd)) {
if (walk->pte_hole)
err = walk->pte_hole(addr, next, walk);
if (err)
break;
continue;
}
/*
* This implies that each ->pmd_entry() handler
* needs to know about pmd_trans_huge() pmds
*/
if (walk->pmd_entry)
err = walk->pmd_entry(pmd, addr, next, walk);
if (err)
break;

/*
* Check this here so we only break down trans_huge
* pages when we _need_ to
*/
if (!walk->pte_entry)
continue;

split_huge_page_pmd(walk->mm, pmd);
if (pmd_none_or_trans_huge_or_clear_bad(pmd))
goto again;
err = walk_pte_range(pmd, addr, next, walk);
if (err)
break;
} while (pmd++, addr = next, addr != end);

return err;
}

static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pud_t *pud;
unsigned long next;
int err = 0;

pud = pud_offset(pgd, addr);
do {
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud)) {
if (walk->pte_hole)
err = walk->pte_hole(addr, next, walk);
if (err)
break;
continue;
}
if (walk->pud_entry)
err = walk->pud_entry(pud, addr, next, walk);
if (!err && (walk->pmd_entry || walk->pte_entry))
err = walk_pmd_range(pud, addr, next, walk);
if (err)
break;
} while (pud++, addr = next, addr != end);

return err;
}

#ifdef CONFIG_HUGETLB_PAGE
static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
unsigned long end)
{
unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
return boundary < end ? boundary : end;
}

static int walk_hugetlb_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct hstate *h = hstate_vma(vma);
unsigned long next;
unsigned long hmask = huge_page_mask(h);
pte_t *pte;
int err = 0;

do {
next = hugetlb_entry_end(h, addr, end);
pte = huge_pte_offset(walk->mm, addr & hmask);
if (pte && walk->hugetlb_entry)
err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
if (err)
return err;
} while (addr = next, addr != end);

return 0;
}

static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
{
struct vm_area_struct *vma;

/* We don't need vma lookup at all. */
if (!walk->hugetlb_entry)
return NULL;

VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
vma = find_vma(walk->mm, addr);
if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))
return vma;

return NULL;
}

#else /* CONFIG_HUGETLB_PAGE */
static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
{
return NULL;
}

static int walk_hugetlb_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
return 0;
}

#endif /* CONFIG_HUGETLB_PAGE */



/**
* walk_page_range - walk a memory map's page tables with a callback
* @addr: starting address
* @end: ending address
* @walk: set of callbacks to invoke for each level of the tree
*
* Recursively walk the page table for the memory area in a VMA,
* calling supplied callbacks. Callbacks are called in-order (first
* PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
* etc.). If lower-level callbacks are omitted, walking depth is reduced.
*
* Each callback receives an entry pointer and the start and end of the
* associated range, and a copy of the original mm_walk for access to
* the ->private or ->mm fields.
*
* Usually no locks are taken, but splitting transparent huge page may
* take page table lock. And the bottom level iterator will map PTE
* directories from highmem if necessary.
*
* If any callback returns a non-zero value, the walk is aborted and
* the return value is propagated back to the caller. Otherwise 0 is returned.
*
* walk->mm->mmap_sem must be held for at least read if walk->hugetlb_entry
* is !NULL.
*/
int walk_page_range(unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
pgd_t *pgd;
unsigned long next;
int err = 0;

if (addr >= end)
return err;

if (!walk->mm)
return -EINVAL;

pgd = pgd_offset(walk->mm, addr);
do {
struct vm_area_struct *vma;

next = pgd_addr_end(addr, end);

/*
* handle hugetlb vma individually because pagetable walk for
* the hugetlb page is dependent on the architecture and
* we can't handled it in the same manner as non-huge pages.
*/
vma = hugetlb_vma(addr, walk);
if (vma) {
if (vma->vm_end < next)
next = vma->vm_end;
/*
* Hugepage is very tightly coupled with vma, so
* walk through hugetlb entries within a given vma.
*/
err = walk_hugetlb_range(vma, addr, next, walk);
if (err)
break;
pgd = pgd_offset(walk->mm, next);
continue;
}

if (pgd_none_or_clear_bad(pgd)) {
if (walk->pte_hole)
err = walk->pte_hole(addr, next, walk);
if (err)
break;
pgd++;
continue;
}
if (walk->pgd_entry)
err = walk->pgd_entry(pgd, addr, next, walk);
if (!err &&
(walk->pud_entry || walk->pmd_entry || walk->pte_entry))
err = walk_pud_range(pgd, addr, next, walk);
if (err)
break;
pgd++;
} while (addr = next, addr != end);

return err;
}
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