mm/page_vma_mapped.c - linux - Git at Google

 // 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_is_match(struct page *page, unsigned long pfn)
 {
 	unsigned long page_pfn = page_to_pfn(page);

 	/* normal page and hugetlbfs page */
 	if (!PageTransCompound(page) || PageHuge(page))
 		return page_pfn == pfn;

 	/* THP can be referenced by any subpage */
 	return pfn >= page_pfn && pfn - page_pfn < thp_nr_pages(page);
 }

 /**
  * check_pte - check if @pvmw->page is mapped at the @pvmw->pte
  * @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking
  *
  * 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_is_match(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.
  *
  * Returns 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(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;
 }
	// 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_is_match(struct page *page, unsigned long pfn)
	{
	unsigned long page_pfn = page_to_pfn(page);

	/* normal page and hugetlbfs page */
	if (!PageTransCompound(page) \|\| PageHuge(page))
	return page_pfn == pfn;

	/* THP can be referenced by any subpage */
	return pfn >= page_pfn && pfn - page_pfn < thp_nr_pages(page);
	}

	/**
	* check_pte - check if @pvmw->page is mapped at the @pvmw->pte
	* @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking
	*
	* 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_is_match(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.
	*
	* Returns 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(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;
	}