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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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d75450ff40
Doug Smythies reports oops with KSM in this backtrace, I've been seeing the same: page_vma_mapped_walk+0xe6/0x5b0 page_referenced_one+0x91/0x1a0 rmap_walk_ksm+0x100/0x190 rmap_walk+0x4f/0x60 page_referenced+0x149/0x170 shrink_active_list+0x1c2/0x430 shrink_node_memcg+0x67a/0x7a0 shrink_node+0xe1/0x320 kswapd+0x34b/0x720 Just as observed in commit4b0ece6fa0
("mm: migrate: fix remove_migration_pte() for ksm pages"), you cannot use page->index calculations on ksm pages. page_vma_mapped_walk() is relying on __vma_address(), where a ksm page can lead it off the end of the page table, and into whatever nonsense is in the next page, ending as an oops inside check_pte()'s pte_page(). KSM tells page_vma_mapped_walk() exactly where to look for the page, it does not need any page->index calculation: and that's so also for all the normal and file and anon pages - just not for THPs and their subpages. Get out early in most cases: instead of a PageKsm test, move down the earlier not-THP-page test, as suggested by Kirill. I'm also slightly worried that this loop can stray into other vmas, so added a vm_end test to prevent surprises; though I have not imagined anything worse than a very contrived case, in which a page mlocked in the next vma might be reclaimed because it is not mlocked in this vma. Fixes:ace71a19ce
("mm: introduce page_vma_mapped_walk()") Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1704031104400.1118@eggly.anvils Signed-off-by: Hugh Dickins <hughd@google.com> Reported-by: Doug Smythies <dsmythies@telus.net> Tested-by: Doug Smythies <dsmythies@telus.net> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
224 lines
5.8 KiB
C
224 lines
5.8 KiB
C
#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 check_pmd(struct page_vma_mapped_walk *pvmw)
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{
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pmd_t pmde;
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/*
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* Make sure we don't re-load pmd between present and !trans_huge check.
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* We need a consistent view.
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*/
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pmde = READ_ONCE(*pvmw->pmd);
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return pmd_present(pmde) && !pmd_trans_huge(pmde);
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}
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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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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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static bool check_pte(struct page_vma_mapped_walk *pvmw)
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{
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if (pvmw->flags & PVMW_MIGRATION) {
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#ifdef CONFIG_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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if (migration_entry_to_page(entry) - pvmw->page >=
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hpage_nr_pages(pvmw->page)) {
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return false;
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}
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if (migration_entry_to_page(entry) < pvmw->page)
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return false;
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#else
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WARN_ON_ONCE(1);
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#endif
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} else {
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if (!pte_present(*pvmw->pte))
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return false;
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/* THP can be referenced by any subpage */
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if (pte_page(*pvmw->pte) - pvmw->page >=
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hpage_nr_pages(pvmw->page)) {
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return false;
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}
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if (pte_page(*pvmw->pte) < pvmw->page)
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return false;
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}
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return true;
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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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pgd_t *pgd;
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p4d_t *p4d;
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pud_t *pud;
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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 (pvmw->pte)
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goto next_pte;
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if (unlikely(PageHuge(pvmw->page))) {
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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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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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restart:
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pgd = pgd_offset(mm, pvmw->address);
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if (!pgd_present(*pgd))
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return false;
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p4d = p4d_offset(pgd, pvmw->address);
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if (!p4d_present(*p4d))
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return false;
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pud = pud_offset(p4d, pvmw->address);
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if (!pud_present(*pud))
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return false;
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pvmw->pmd = pmd_offset(pud, pvmw->address);
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if (pmd_trans_huge(*pvmw->pmd)) {
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pvmw->ptl = pmd_lock(mm, pvmw->pmd);
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if (!pmd_present(*pvmw->pmd))
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return not_found(pvmw);
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if (likely(pmd_trans_huge(*pvmw->pmd))) {
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if (pvmw->flags & PVMW_MIGRATION)
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return not_found(pvmw);
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if (pmd_page(*pvmw->pmd) != page)
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return not_found(pvmw);
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return true;
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} else {
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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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}
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} else {
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if (!check_pmd(pvmw))
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return false;
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}
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if (!map_pte(pvmw))
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goto next_pte;
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while (1) {
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if (check_pte(pvmw))
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return true;
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next_pte:
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/* Seek to next pte only makes sense for THP */
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if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page))
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return not_found(pvmw);
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do {
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pvmw->address += PAGE_SIZE;
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if (pvmw->address >= pvmw->vma->vm_end ||
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pvmw->address >=
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__vma_address(pvmw->page, pvmw->vma) +
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hpage_nr_pages(pvmw->page) * PAGE_SIZE)
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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 == 0) {
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pte_unmap(pvmw->pte);
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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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goto restart;
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} else {
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pvmw->pte++;
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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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}
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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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unsigned long start, end;
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start = __vma_address(page, vma);
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end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
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if (unlikely(end < vma->vm_start || start >= vma->vm_end))
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return 0;
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pvmw.address = max(start, vma->vm_start);
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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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