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![Hugh Dickins](/assets/img/avatar_default.png)
[ Upstream commita7a69d8ba8
] Aha! Shouldn't that quick scan over pte_none()s make sure that it holds ptlock in the PVMW_SYNC case? That too might have been responsible for BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though I've never seen any. Link: https://lkml.kernel.org/r/1bdf384c-8137-a149-2a1e-475a4791c3c@google.com Link: https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ Fixes:ace71a19ce
("mm: introduce page_vma_mapped_walk()") Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Tested-by: Wang Yugui <wangyugui@e16-tech.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
314 lines
8.4 KiB
C
314 lines
8.4 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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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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*
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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 arbitrary
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* 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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return false;
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pfn = migration_entry_to_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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return false;
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pfn = device_private_entry_to_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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if (pfn < page_to_pfn(pvmw->page))
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return false;
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/* THP can be referenced by any subpage */
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if (pfn - page_to_pfn(pvmw->page) >= hpage_nr_pages(pvmw->page))
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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->page 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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* Retruns 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 mm_struct *mm = pvmw->vma->vm_mm;
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struct page *page = pvmw->page;
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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(PageHuge(page))) {
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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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/* when pud is not present, pte will be NULL */
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pvmw->pte = huge_pte_offset(mm, pvmw->address,
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PAGE_SIZE << compound_order(page));
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if (!pvmw->pte)
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return false;
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pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
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spin_lock(pvmw->ptl);
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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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/*
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* Seek to next pte only makes sense for THP.
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* But more important than that optimization, is to filter out
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* any PageKsm page: whose page->index misleads vma_address()
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* and vma_address_end() to disaster.
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*/
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end = PageTransCompound(page) ?
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vma_address_end(page, pvmw->vma) :
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pvmw->address + PAGE_SIZE;
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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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pvmw->ptl = pmd_lock(mm, pvmw->pmd);
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pmde = *pvmw->pmd;
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if (likely(pmd_trans_huge(pmde))) {
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if (pvmw->flags & PVMW_MIGRATION)
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return not_found(pvmw);
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if (pmd_page(pmde) != page)
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return not_found(pvmw);
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return true;
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}
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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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migration_entry_to_page(entry) != page)
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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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PageTransCompound(page)) {
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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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.page = page,
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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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