Пример #1
0
/**
 * follow_page_mask - look up a page descriptor from a user-virtual address
 * @vma: vm_area_struct mapping @address
 * @address: virtual address to look up
 * @flags: flags modifying lookup behaviour
 * @page_mask: on output, *page_mask is set according to the size of the page
 *
 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 *
 * Returns the mapped (struct page *), %NULL if no mapping exists, or
 * an error pointer if there is a mapping to something not represented
 * by a page descriptor (see also vm_normal_page()).
 */
struct page *follow_page_mask(struct vm_area_struct *vma,
			      unsigned long address, unsigned int flags,
			      unsigned int *page_mask)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

	*page_mask = 0;

	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
	if (!IS_ERR(page)) {
		BUG_ON(flags & FOLL_GET);
		return page;
	}

	pgd = pgd_offset(mm, address);
	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
		return no_page_table(vma, flags);

	pud = pud_offset(pgd, address);
	if (pud_none(*pud))
		return no_page_table(vma, flags);
	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
		if (flags & FOLL_GET)
			return NULL;
		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
		return page;
	}
	if (unlikely(pud_bad(*pud)))
		return no_page_table(vma, flags);

	pmd = pmd_offset(pud, address);
	if (pmd_none(*pmd))
		return no_page_table(vma, flags);
	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
		if (flags & FOLL_GET) {
			/*
			 * Refcount on tail pages are not well-defined and
			 * shouldn't be taken. The caller should handle a NULL
			 * return when trying to follow tail pages.
			 */
			if (PageHead(page))
				get_page(page);
			else
				page = NULL;
		}
		return page;
	}
	if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
		return no_page_table(vma, flags);
	if (pmd_trans_huge(*pmd)) {
		if (flags & FOLL_SPLIT) {
			split_huge_page_pmd(vma, address, pmd);
			return follow_page_pte(vma, address, pmd, flags);
		}
		ptl = pmd_lock(mm, pmd);
		if (likely(pmd_trans_huge(*pmd))) {
			if (unlikely(pmd_trans_splitting(*pmd))) {
				spin_unlock(ptl);
				wait_split_huge_page(vma->anon_vma, pmd);
			} else {
				page = follow_trans_huge_pmd(vma, address,
							     pmd, flags);
				spin_unlock(ptl);
				*page_mask = HPAGE_PMD_NR - 1;
				return page;
			}
		} else
			spin_unlock(ptl);
	}
	return follow_page_pte(vma, address, pmd, flags);
}
Пример #2
0
/**
 * follow_page_mask - look up a page descriptor from a user-virtual address
 * @vma: vm_area_struct mapping @address
 * @address: virtual address to look up
 * @flags: flags modifying lookup behaviour
 * @page_mask: on output, *page_mask is set according to the size of the page
 *
 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 *
 * Returns the mapped (struct page *), %NULL if no mapping exists, or
 * an error pointer if there is a mapping to something not represented
 * by a page descriptor (see also vm_normal_page()).
 */
struct page *follow_page_mask(struct vm_area_struct *vma,
			      unsigned long address, unsigned int flags,
			      unsigned int *page_mask)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

	*page_mask = 0;

	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
	if (!IS_ERR(page)) {
		BUG_ON(flags & FOLL_GET);
		return page;
	}

	pgd = pgd_offset(mm, address);
	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
		return no_page_table(vma, flags);

	pud = pud_offset(pgd, address);
	if (pud_none(*pud))
		return no_page_table(vma, flags);
	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
		page = follow_huge_pud(mm, address, pud, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
	if (unlikely(pud_bad(*pud)))
		return no_page_table(vma, flags);

	pmd = pmd_offset(pud, address);
	if (pmd_none(*pmd))
		return no_page_table(vma, flags);
	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
		page = follow_huge_pmd(mm, address, pmd, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
		return no_page_table(vma, flags);
	if (pmd_trans_huge(*pmd)) {
		if (flags & FOLL_SPLIT) {
			split_huge_page_pmd(vma, address, pmd);
			return follow_page_pte(vma, address, pmd, flags);
		}
		ptl = pmd_lock(mm, pmd);
		if (likely(pmd_trans_huge(*pmd))) {
			if (unlikely(pmd_trans_splitting(*pmd))) {
				spin_unlock(ptl);
				wait_split_huge_page(vma->anon_vma, pmd);
			} else {
				page = follow_trans_huge_pmd(vma, address,
							     pmd, flags);
				spin_unlock(ptl);
				*page_mask = HPAGE_PMD_NR - 1;
				return page;
			}
		} else
			spin_unlock(ptl);
	}
	return follow_page_pte(vma, address, pmd, flags);
}