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-rw-r--r--mm/page_vma_mapped.c315
1 files changed, 315 insertions, 0 deletions
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
new file mode 100644
index 000000000..edca78609
--- /dev/null
+++ b/mm/page_vma_mapped.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/mm.h>
+#include <linux/rmap.h>
+#include <linux/hugetlb.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+
+#include "internal.h"
+
+static inline bool not_found(struct page_vma_mapped_walk *pvmw)
+{
+ page_vma_mapped_walk_done(pvmw);
+ return false;
+}
+
+static bool map_pte(struct page_vma_mapped_walk *pvmw)
+{
+ pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
+ if (!(pvmw->flags & PVMW_SYNC)) {
+ if (pvmw->flags & PVMW_MIGRATION) {
+ if (!is_swap_pte(*pvmw->pte))
+ return false;
+ } else {
+ /*
+ * We get here when we are trying to unmap a private
+ * device page from the process address space. Such
+ * page is not CPU accessible and thus is mapped as
+ * a special swap entry, nonetheless it still does
+ * count as a valid regular mapping for the page (and
+ * is accounted as such in page maps count).
+ *
+ * So handle this special case as if it was a normal
+ * page mapping ie lock CPU page table and returns
+ * true.
+ *
+ * For more details on device private memory see HMM
+ * (include/linux/hmm.h or mm/hmm.c).
+ */
+ if (is_swap_pte(*pvmw->pte)) {
+ swp_entry_t entry;
+
+ /* Handle un-addressable ZONE_DEVICE memory */
+ entry = pte_to_swp_entry(*pvmw->pte);
+ if (!is_device_private_entry(entry))
+ return false;
+ } else if (!pte_present(*pvmw->pte))
+ return false;
+ }
+ }
+ pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
+ spin_lock(pvmw->ptl);
+ return true;
+}
+
+static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn)
+{
+ unsigned long hpage_pfn = page_to_pfn(hpage);
+
+ /* THP can be referenced by any subpage */
+ return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage);
+}
+
+/**
+ * check_pte - check if @pvmw->page is mapped at the @pvmw->pte
+ *
+ * page_vma_mapped_walk() found a place where @pvmw->page is *potentially*
+ * mapped. check_pte() has to validate this.
+ *
+ * @pvmw->pte may point to empty PTE, swap PTE or PTE pointing to arbitrary
+ * page.
+ *
+ * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
+ * entry that points to @pvmw->page or any subpage in case of THP.
+ *
+ * If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to
+ * @pvmw->page or any subpage in case of THP.
+ *
+ * Otherwise, return false.
+ *
+ */
+static bool check_pte(struct page_vma_mapped_walk *pvmw)
+{
+ unsigned long pfn;
+
+ if (pvmw->flags & PVMW_MIGRATION) {
+ swp_entry_t entry;
+ if (!is_swap_pte(*pvmw->pte))
+ return false;
+ entry = pte_to_swp_entry(*pvmw->pte);
+
+ if (!is_migration_entry(entry))
+ return false;
+
+ pfn = migration_entry_to_pfn(entry);
+ } else if (is_swap_pte(*pvmw->pte)) {
+ swp_entry_t entry;
+
+ /* Handle un-addressable ZONE_DEVICE memory */
+ entry = pte_to_swp_entry(*pvmw->pte);
+ if (!is_device_private_entry(entry))
+ return false;
+
+ pfn = device_private_entry_to_pfn(entry);
+ } else {
+ if (!pte_present(*pvmw->pte))
+ return false;
+
+ pfn = pte_pfn(*pvmw->pte);
+ }
+
+ return pfn_in_hpage(pvmw->page, pfn);
+}
+
+static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
+{
+ pvmw->address = (pvmw->address + size) & ~(size - 1);
+ if (!pvmw->address)
+ pvmw->address = ULONG_MAX;
+}
+
+/**
+ * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at
+ * @pvmw->address
+ * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
+ * must be set. pmd, pte and ptl must be NULL.
+ *
+ * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
+ * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
+ * adjusted if needed (for PTE-mapped THPs).
+ *
+ * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
+ * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
+ * a loop to find all PTEs that map the THP.
+ *
+ * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
+ * regardless of which page table level the page is mapped at. @pvmw->pmd is
+ * NULL.
+ *
+ * Retruns false if there are no more page table entries for the page in
+ * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
+ *
+ * If you need to stop the walk before page_vma_mapped_walk() returned false,
+ * use page_vma_mapped_walk_done(). It will do the housekeeping.
+ */
+bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
+{
+ struct mm_struct *mm = pvmw->vma->vm_mm;
+ struct page *page = pvmw->page;
+ unsigned long end;
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t pmde;
+
+ /* The only possible pmd mapping has been handled on last iteration */
+ if (pvmw->pmd && !pvmw->pte)
+ return not_found(pvmw);
+
+ if (unlikely(PageHuge(page))) {
+ /* The only possible mapping was handled on last iteration */
+ if (pvmw->pte)
+ return not_found(pvmw);
+
+ /* when pud is not present, pte will be NULL */
+ pvmw->pte = huge_pte_offset(mm, pvmw->address,
+ PAGE_SIZE << compound_order(page));
+ if (!pvmw->pte)
+ return false;
+
+ pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
+ spin_lock(pvmw->ptl);
+ if (!check_pte(pvmw))
+ return not_found(pvmw);
+ return true;
+ }
+
+ /*
+ * Seek to next pte only makes sense for THP.
+ * But more important than that optimization, is to filter out
+ * any PageKsm page: whose page->index misleads vma_address()
+ * and vma_address_end() to disaster.
+ */
+ end = PageTransCompound(page) ?
+ vma_address_end(page, pvmw->vma) :
+ pvmw->address + PAGE_SIZE;
+ if (pvmw->pte)
+ goto next_pte;
+restart:
+ do {
+ pgd = pgd_offset(mm, pvmw->address);
+ if (!pgd_present(*pgd)) {
+ step_forward(pvmw, PGDIR_SIZE);
+ continue;
+ }
+ p4d = p4d_offset(pgd, pvmw->address);
+ if (!p4d_present(*p4d)) {
+ step_forward(pvmw, P4D_SIZE);
+ continue;
+ }
+ pud = pud_offset(p4d, pvmw->address);
+ if (!pud_present(*pud)) {
+ step_forward(pvmw, PUD_SIZE);
+ continue;
+ }
+
+ pvmw->pmd = pmd_offset(pud, pvmw->address);
+ /*
+ * Make sure the pmd value isn't cached in a register by the
+ * compiler and used as a stale value after we've observed a
+ * subsequent update.
+ */
+ pmde = READ_ONCE(*pvmw->pmd);
+
+ if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
+ pvmw->ptl = pmd_lock(mm, pvmw->pmd);
+ pmde = *pvmw->pmd;
+ if (likely(pmd_trans_huge(pmde))) {
+ if (pvmw->flags & PVMW_MIGRATION)
+ return not_found(pvmw);
+ if (pmd_page(pmde) != page)
+ return not_found(pvmw);
+ return true;
+ }
+ if (!pmd_present(pmde)) {
+ swp_entry_t entry;
+
+ if (!thp_migration_supported() ||
+ !(pvmw->flags & PVMW_MIGRATION))
+ return not_found(pvmw);
+ entry = pmd_to_swp_entry(pmde);
+ if (!is_migration_entry(entry) ||
+ migration_entry_to_page(entry) != page)
+ return not_found(pvmw);
+ return true;
+ }
+ /* THP pmd was split under us: handle on pte level */
+ spin_unlock(pvmw->ptl);
+ pvmw->ptl = NULL;
+ } else if (!pmd_present(pmde)) {
+ /*
+ * If PVMW_SYNC, take and drop THP pmd lock so that we
+ * cannot return prematurely, while zap_huge_pmd() has
+ * cleared *pmd but not decremented compound_mapcount().
+ */
+ if ((pvmw->flags & PVMW_SYNC) &&
+ PageTransCompound(page)) {
+ spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
+
+ spin_unlock(ptl);
+ }
+ step_forward(pvmw, PMD_SIZE);
+ continue;
+ }
+ if (!map_pte(pvmw))
+ goto next_pte;
+this_pte:
+ if (check_pte(pvmw))
+ return true;
+next_pte:
+ do {
+ pvmw->address += PAGE_SIZE;
+ if (pvmw->address >= end)
+ return not_found(pvmw);
+ /* Did we cross page table boundary? */
+ if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
+ if (pvmw->ptl) {
+ spin_unlock(pvmw->ptl);
+ pvmw->ptl = NULL;
+ }
+ pte_unmap(pvmw->pte);
+ pvmw->pte = NULL;
+ goto restart;
+ }
+ pvmw->pte++;
+ if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
+ pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
+ spin_lock(pvmw->ptl);
+ }
+ } while (pte_none(*pvmw->pte));
+
+ if (!pvmw->ptl) {
+ pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
+ spin_lock(pvmw->ptl);
+ }
+ goto this_pte;
+ } while (pvmw->address < end);
+
+ return false;
+}
+
+/**
+ * page_mapped_in_vma - check whether a page is really mapped in a VMA
+ * @page: the page to test
+ * @vma: the VMA to test
+ *
+ * Returns 1 if the page is mapped into the page tables of the VMA, 0
+ * if the page is not mapped into the page tables of this VMA. Only
+ * valid for normal file or anonymous VMAs.
+ */
+int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
+{
+ struct page_vma_mapped_walk pvmw = {
+ .page = page,
+ .vma = vma,
+ .flags = PVMW_SYNC,
+ };
+
+ pvmw.address = vma_address(page, vma);
+ if (pvmw.address == -EFAULT)
+ return 0;
+ if (!page_vma_mapped_walk(&pvmw))
+ return 0;
+ page_vma_mapped_walk_done(&pvmw);
+ return 1;
+}
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