320 lines
8.7 KiB
C
320 lines
8.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/mm.h>
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#include <linux/rmap.h>
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#include <linux/hugetlb.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include "internal.h"
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static inline bool not_found(struct page_vma_mapped_walk *pvmw)
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{
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page_vma_mapped_walk_done(pvmw);
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return false;
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}
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static bool map_pte(struct page_vma_mapped_walk *pvmw)
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{
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pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
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if (!(pvmw->flags & PVMW_SYNC)) {
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if (pvmw->flags & PVMW_MIGRATION) {
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if (!is_swap_pte(*pvmw->pte))
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return false;
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} else {
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/*
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* We get here when we are trying to unmap a private
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* device page from the process address space. Such
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* page is not CPU accessible and thus is mapped as
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* a special swap entry, nonetheless it still does
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* count as a valid regular mapping for the page (and
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* is accounted as such in page maps count).
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*
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* So handle this special case as if it was a normal
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* page mapping ie lock CPU page table and returns
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* true.
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*
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* For more details on device private memory see HMM
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* (include/linux/hmm.h or mm/hmm.c).
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*/
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if (is_swap_pte(*pvmw->pte)) {
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swp_entry_t entry;
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/* Handle un-addressable ZONE_DEVICE memory */
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entry = pte_to_swp_entry(*pvmw->pte);
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if (!is_device_private_entry(entry) &&
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!is_device_exclusive_entry(entry))
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return false;
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} else if (!pte_present(*pvmw->pte))
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return false;
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}
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}
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pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
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spin_lock(pvmw->ptl);
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return true;
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}
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/**
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* check_pte - check if @pvmw->page is mapped at the @pvmw->pte
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* @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking
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*
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* page_vma_mapped_walk() found a place where @pvmw->page is *potentially*
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* mapped. check_pte() has to validate this.
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*
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* pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
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* arbitrary page.
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*
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* If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
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* entry that points to @pvmw->page or any subpage in case of THP.
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*
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* If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
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* pvmw->page or any subpage in case of THP.
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*
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* Otherwise, return false.
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*
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*/
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static bool check_pte(struct page_vma_mapped_walk *pvmw)
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{
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unsigned long pfn;
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if (pvmw->flags & PVMW_MIGRATION) {
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swp_entry_t entry;
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if (!is_swap_pte(*pvmw->pte))
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return false;
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entry = pte_to_swp_entry(*pvmw->pte);
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if (!is_migration_entry(entry) &&
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!is_device_exclusive_entry(entry))
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return false;
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pfn = swp_offset_pfn(entry);
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} else if (is_swap_pte(*pvmw->pte)) {
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swp_entry_t entry;
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/* Handle un-addressable ZONE_DEVICE memory */
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entry = pte_to_swp_entry(*pvmw->pte);
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if (!is_device_private_entry(entry) &&
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!is_device_exclusive_entry(entry))
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return false;
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pfn = swp_offset_pfn(entry);
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} else {
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if (!pte_present(*pvmw->pte))
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return false;
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pfn = pte_pfn(*pvmw->pte);
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}
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return (pfn - pvmw->pfn) < pvmw->nr_pages;
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}
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/* Returns true if the two ranges overlap. Careful to not overflow. */
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static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
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{
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if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
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return false;
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if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
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return false;
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return true;
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}
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static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
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{
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pvmw->address = (pvmw->address + size) & ~(size - 1);
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if (!pvmw->address)
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pvmw->address = ULONG_MAX;
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}
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/**
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* page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
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* @pvmw->address
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* @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
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* must be set. pmd, pte and ptl must be NULL.
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*
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* Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
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* to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
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* adjusted if needed (for PTE-mapped THPs).
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*
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* If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
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* (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
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* a loop to find all PTEs that map the THP.
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*
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* For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
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* regardless of which page table level the page is mapped at. @pvmw->pmd is
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* NULL.
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*
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* Returns false if there are no more page table entries for the page in
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* the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
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*
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* If you need to stop the walk before page_vma_mapped_walk() returned false,
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* use page_vma_mapped_walk_done(). It will do the housekeeping.
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*/
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bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
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{
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struct vm_area_struct *vma = pvmw->vma;
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struct mm_struct *mm = vma->vm_mm;
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unsigned long end;
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pgd_t *pgd;
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p4d_t *p4d;
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pud_t *pud;
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pmd_t pmde;
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/* The only possible pmd mapping has been handled on last iteration */
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if (pvmw->pmd && !pvmw->pte)
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return not_found(pvmw);
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if (unlikely(is_vm_hugetlb_page(vma))) {
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struct hstate *hstate = hstate_vma(vma);
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unsigned long size = huge_page_size(hstate);
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/* The only possible mapping was handled on last iteration */
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if (pvmw->pte)
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return not_found(pvmw);
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/*
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* All callers that get here will already hold the
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* i_mmap_rwsem. Therefore, no additional locks need to be
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* taken before calling hugetlb_walk().
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*/
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pvmw->pte = hugetlb_walk(vma, pvmw->address, size);
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if (!pvmw->pte)
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return false;
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pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
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if (!check_pte(pvmw))
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return not_found(pvmw);
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return true;
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}
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end = vma_address_end(pvmw);
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if (pvmw->pte)
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goto next_pte;
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restart:
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do {
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pgd = pgd_offset(mm, pvmw->address);
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if (!pgd_present(*pgd)) {
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step_forward(pvmw, PGDIR_SIZE);
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continue;
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}
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p4d = p4d_offset(pgd, pvmw->address);
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if (!p4d_present(*p4d)) {
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step_forward(pvmw, P4D_SIZE);
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continue;
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}
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pud = pud_offset(p4d, pvmw->address);
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if (!pud_present(*pud)) {
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step_forward(pvmw, PUD_SIZE);
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continue;
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}
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pvmw->pmd = pmd_offset(pud, pvmw->address);
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/*
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* Make sure the pmd value isn't cached in a register by the
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* compiler and used as a stale value after we've observed a
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* subsequent update.
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*/
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pmde = READ_ONCE(*pvmw->pmd);
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if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
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(pmd_present(pmde) && pmd_devmap(pmde))) {
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pvmw->ptl = pmd_lock(mm, pvmw->pmd);
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pmde = *pvmw->pmd;
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if (!pmd_present(pmde)) {
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swp_entry_t entry;
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if (!thp_migration_supported() ||
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!(pvmw->flags & PVMW_MIGRATION))
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return not_found(pvmw);
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entry = pmd_to_swp_entry(pmde);
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if (!is_migration_entry(entry) ||
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!check_pmd(swp_offset_pfn(entry), pvmw))
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return not_found(pvmw);
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return true;
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}
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if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
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if (pvmw->flags & PVMW_MIGRATION)
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return not_found(pvmw);
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if (!check_pmd(pmd_pfn(pmde), pvmw))
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return not_found(pvmw);
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return true;
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}
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/* THP pmd was split under us: handle on pte level */
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spin_unlock(pvmw->ptl);
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pvmw->ptl = NULL;
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} else if (!pmd_present(pmde)) {
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/*
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* If PVMW_SYNC, take and drop THP pmd lock so that we
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* cannot return prematurely, while zap_huge_pmd() has
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* cleared *pmd but not decremented compound_mapcount().
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*/
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if ((pvmw->flags & PVMW_SYNC) &&
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transhuge_vma_suitable(vma, pvmw->address) &&
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(pvmw->nr_pages >= HPAGE_PMD_NR)) {
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spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
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spin_unlock(ptl);
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}
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step_forward(pvmw, PMD_SIZE);
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continue;
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}
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if (!map_pte(pvmw))
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goto next_pte;
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this_pte:
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if (check_pte(pvmw))
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return true;
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next_pte:
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do {
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pvmw->address += PAGE_SIZE;
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if (pvmw->address >= end)
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return not_found(pvmw);
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/* Did we cross page table boundary? */
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if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
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if (pvmw->ptl) {
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spin_unlock(pvmw->ptl);
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pvmw->ptl = NULL;
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}
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pte_unmap(pvmw->pte);
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pvmw->pte = NULL;
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goto restart;
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}
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pvmw->pte++;
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if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
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pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
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spin_lock(pvmw->ptl);
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}
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} while (pte_none(*pvmw->pte));
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if (!pvmw->ptl) {
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pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
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spin_lock(pvmw->ptl);
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}
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goto this_pte;
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} while (pvmw->address < end);
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return false;
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}
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/**
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* page_mapped_in_vma - check whether a page is really mapped in a VMA
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* @page: the page to test
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* @vma: the VMA to test
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*
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* Returns 1 if the page is mapped into the page tables of the VMA, 0
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* if the page is not mapped into the page tables of this VMA. Only
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* valid for normal file or anonymous VMAs.
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*/
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int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
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{
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struct page_vma_mapped_walk pvmw = {
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.pfn = page_to_pfn(page),
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.nr_pages = 1,
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.vma = vma,
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.flags = PVMW_SYNC,
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};
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pvmw.address = vma_address(page, vma);
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if (pvmw.address == -EFAULT)
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return 0;
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if (!page_vma_mapped_walk(&pvmw))
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return 0;
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page_vma_mapped_walk_done(&pvmw);
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return 1;
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}
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