[mirror_ubuntu-bionic-kernel.git] / mm / page_vma_mapped.c

// 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 {
			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);
}

/**
 * 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;
	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 (pvmw->pte)
		goto next_pte;

	if (unlikely(PageHuge(pvmw->page))) {
		/* 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;
	}
restart:
	pgd = pgd_offset(mm, pvmw->address);
	if (!pgd_present(*pgd))
		return false;
	p4d = p4d_offset(pgd, pvmw->address);
	if (!p4d_present(*p4d))
		return false;
	pud = pud_offset(p4d, pvmw->address);
	if (!pud_present(*pud))
		return false;
	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);
		if (likely(pmd_trans_huge(*pvmw->pmd))) {
			if (pvmw->flags & PVMW_MIGRATION)
				return not_found(pvmw);
			if (pmd_page(*pvmw->pmd) != page)
				return not_found(pvmw);
			return true;
		} else if (!pmd_present(*pvmw->pmd)) {
			if (thp_migration_supported()) {
				if (!(pvmw->flags & PVMW_MIGRATION))
					return not_found(pvmw);
				if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) {
					swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd);

					if (migration_entry_to_page(entry) != page)
						return not_found(pvmw);
					return true;
				}
			}
			return not_found(pvmw);
		} else {
			/* THP pmd was split under us: handle on pte level */
			spin_unlock(pvmw->ptl);
			pvmw->ptl = NULL;
		}
	} else if (!pmd_present(pmde)) {
		return false;
	}
	if (!map_pte(pvmw))
		goto next_pte;
	while (1) {
		if (check_pte(pvmw))
			return true;
next_pte:
		/* Seek to next pte only makes sense for THP */
		if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page))
			return not_found(pvmw);
		do {
			pvmw->address += PAGE_SIZE;
			if (pvmw->address >= pvmw->vma->vm_end ||
			    pvmw->address >=
					__vma_address(pvmw->page, pvmw->vma) +
					hpage_nr_pages(pvmw->page) * PAGE_SIZE)
				return not_found(pvmw);
			/* Did we cross page table boundary? */
			if (pvmw->address % PMD_SIZE == 0) {
				pte_unmap(pvmw->pte);
				if (pvmw->ptl) {
					spin_unlock(pvmw->ptl);
					pvmw->ptl = NULL;
				}
				goto restart;
			} else {
				pvmw->pte++;
			}
		} while (pte_none(*pvmw->pte));

		if (!pvmw->ptl) {
			pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
			spin_lock(pvmw->ptl);
		}
	}
}

/**
 * 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,
	};
	unsigned long start, end;

	start = __vma_address(page, vma);
	end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);

	if (unlikely(end < vma->vm_start || start >= vma->vm_end))
		return 0;
	pvmw.address = max(start, vma->vm_start);
	if (!page_vma_mapped_walk(&pvmw))
		return 0;
	page_vma_mapped_walk_done(&pvmw);
	return 1;
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
ace71a19 KS	2	#include <linux/mm.h>
	3	#include <linux/rmap.h>
	4	#include <linux/hugetlb.h>
	5	#include <linux/swap.h>
	6	#include <linux/swapops.h>
	7
	8	#include "internal.h"
	9
ace71a19 KS	10	static inline bool not_found(struct page_vma_mapped_walk *pvmw)
	11	{
	12	page_vma_mapped_walk_done(pvmw);
	13	return false;
	14	}
	15
	16	static bool map_pte(struct page_vma_mapped_walk *pvmw)
	17	{
	18	pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
	19	if (!(pvmw->flags & PVMW_SYNC)) {
	20	if (pvmw->flags & PVMW_MIGRATION) {
	21	if (!is_swap_pte(*pvmw->pte))
	22	return false;
	23	} else {
	24	if (!pte_present(*pvmw->pte))
	25	return false;
	26	}
	27	}
	28	pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
	29	spin_lock(pvmw->ptl);
	30	return true;
	31	}
	32
7222708e KS	33	static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn)
	34	{
	35	unsigned long hpage_pfn = page_to_pfn(hpage);
	36
	37	/* THP can be referenced by any subpage */
	38	return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage);
	39	}
	40
0d665e7b KS	41	/**
	42	* check_pte - check if @pvmw->page is mapped at the @pvmw->pte
	43	*
	44	* page_vma_mapped_walk() found a place where @pvmw->page is potentially
	45	* mapped. check_pte() has to validate this.
	46	*
	47	* @pvmw->pte may point to empty PTE, swap PTE or PTE pointing to arbitrary
	48	* page.
	49	*
	50	* If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
	51	* entry that points to @pvmw->page or any subpage in case of THP.
	52	*
	53	* If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to
	54	* @pvmw->page or any subpage in case of THP.
	55	*
	56	* Otherwise, return false.
	57	*
	58	*/
ace71a19 KS	59	static bool check_pte(struct page_vma_mapped_walk *pvmw)
ace71a19 KS	60	{
0d665e7b KS	61	unsigned long pfn;
0d665e7b KS	62
ace71a19	63	if (pvmw->flags & PVMW_MIGRATION) {
ace71a19 KS	64	swp_entry_t entry;
	65	if (!is_swap_pte(*pvmw->pte))
	66	return false;
	67	entry = pte_to_swp_entry(*pvmw->pte);
a5430dda	68
ace71a19 KS	69	if (!is_migration_entry(entry))
ace71a19 KS	70	return false;
a5430dda	71
0d665e7b KS	72	pfn = migration_entry_to_pfn(entry);
	73	} else if (is_swap_pte(*pvmw->pte)) {
	74	swp_entry_t entry;
a5430dda	75
0d665e7b KS	76	/* Handle un-addressable ZONE_DEVICE memory */
	77	entry = pte_to_swp_entry(*pvmw->pte);
	78	if (!is_device_private_entry(entry))
ace71a19 KS	79	return false;
ace71a19 KS	80
0d665e7b KS	81	pfn = device_private_entry_to_pfn(entry);
	82	} else {
	83	if (!pte_present(*pvmw->pte))
ace71a19	84	return false;
0d665e7b KS	85
0d665e7b KS	86	pfn = pte_pfn(*pvmw->pte);
ace71a19 KS	87	}
ace71a19 KS	88
7222708e	89	return pfn_in_hpage(pvmw->page, pfn);
ace71a19 KS	90	}
	91
	92	/**
	93	* page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at
	94	* @pvmw->address
	95	* @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
	96	* must be set. pmd, pte and ptl must be NULL.
	97	*
	98	* Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
	99	* to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
	100	* adjusted if needed (for PTE-mapped THPs).
	101	*
	102	* If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
	103	* (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
	104	* a loop to find all PTEs that map the THP.
	105	*
	106	* For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
	107	* regardless of which page table level the page is mapped at. @pvmw->pmd is
	108	* NULL.
	109	*
	110	* Retruns false if there are no more page table entries for the page in
	111	* the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
	112	*
	113	* If you need to stop the walk before page_vma_mapped_walk() returned false,
	114	* use page_vma_mapped_walk_done(). It will do the housekeeping.
	115	*/
	116	bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
	117	{
	118	struct mm_struct *mm = pvmw->vma->vm_mm;
	119	struct page *page = pvmw->page;
	120	pgd_t *pgd;
c2febafc	121	p4d_t *p4d;
ace71a19	122	pud_t *pud;
a7b10095	123	pmd_t pmde;
ace71a19 KS	124
	125	/* The only possible pmd mapping has been handled on last iteration */
	126	if (pvmw->pmd && !pvmw->pte)
	127	return not_found(pvmw);
	128
d75450ff	129	if (pvmw->pte)
ace71a19	130	goto next_pte;
ace71a19 KS	131
	132	if (unlikely(PageHuge(pvmw->page))) {
	133	/* when pud is not present, pte will be NULL */
7868a208 PA	134	pvmw->pte = huge_pte_offset(mm, pvmw->address,
7868a208 PA	135	PAGE_SIZE << compound_order(page));
ace71a19 KS	136	if (!pvmw->pte)
	137	return false;
	138
	139	pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
	140	spin_lock(pvmw->ptl);
	141	if (!check_pte(pvmw))
	142	return not_found(pvmw);
	143	return true;
	144	}
	145	restart:
	146	pgd = pgd_offset(mm, pvmw->address);
	147	if (!pgd_present(*pgd))
	148	return false;
c2febafc KS	149	p4d = p4d_offset(pgd, pvmw->address);
	150	if (!p4d_present(*p4d))
	151	return false;
	152	pud = pud_offset(p4d, pvmw->address);
ace71a19 KS	153	if (!pud_present(*pud))
	154	return false;
	155	pvmw->pmd = pmd_offset(pud, pvmw->address);
a7b10095 WD	156	/*
	157	* Make sure the pmd value isn't cached in a register by the
	158	* compiler and used as a stale value after we've observed a
	159	* subsequent update.
	160	*/
	161	pmde = READ_ONCE(*pvmw->pmd);
	162	if (pmd_trans_huge(pmde) \|\| is_pmd_migration_entry(pmde)) {
ace71a19	163	pvmw->ptl = pmd_lock(mm, pvmw->pmd);
ace71a19 KS	164	if (likely(pmd_trans_huge(*pvmw->pmd))) {
	165	if (pvmw->flags & PVMW_MIGRATION)
	166	return not_found(pvmw);
	167	if (pmd_page(*pvmw->pmd) != page)
	168	return not_found(pvmw);
	169	return true;
616b8371 ZY	170	} else if (!pmd_present(*pvmw->pmd)) {
	171	if (thp_migration_supported()) {
	172	if (!(pvmw->flags & PVMW_MIGRATION))
	173	return not_found(pvmw);
	174	if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) {
	175	swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd);
	176
	177	if (migration_entry_to_page(entry) != page)
	178	return not_found(pvmw);
	179	return true;
	180	}
af0db981	181	}
616b8371	182	return not_found(pvmw);
ace71a19 KS	183	} else {
	184	/* THP pmd was split under us: handle on pte level */
	185	spin_unlock(pvmw->ptl);
	186	pvmw->ptl = NULL;
	187	}
a7b10095 WD	188	} else if (!pmd_present(pmde)) {
a7b10095 WD	189	return false;
ace71a19 KS	190	}
	191	if (!map_pte(pvmw))
	192	goto next_pte;
	193	while (1) {
	194	if (check_pte(pvmw))
	195	return true;
d75450ff HD	196	next_pte:
	197	/* Seek to next pte only makes sense for THP */
	198	if (!PageTransHuge(pvmw->page) \|\| PageHuge(pvmw->page))
	199	return not_found(pvmw);
	200	do {
ace71a19	201	pvmw->address += PAGE_SIZE;
d75450ff HD	202	if (pvmw->address >= pvmw->vma->vm_end \|\|
d75450ff HD	203	pvmw->address >=
ace71a19 KS	204	__vma_address(pvmw->page, pvmw->vma) +
	205	hpage_nr_pages(pvmw->page) * PAGE_SIZE)
	206	return not_found(pvmw);
	207	/* Did we cross page table boundary? */
	208	if (pvmw->address % PMD_SIZE == 0) {
	209	pte_unmap(pvmw->pte);
	210	if (pvmw->ptl) {
	211	spin_unlock(pvmw->ptl);
	212	pvmw->ptl = NULL;
	213	}
	214	goto restart;
	215	} else {
	216	pvmw->pte++;
	217	}
	218	} while (pte_none(*pvmw->pte));
	219
	220	if (!pvmw->ptl) {
	221	pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
	222	spin_lock(pvmw->ptl);
	223	}
	224	}
	225	}
6a328a62 KS	226
	227	/**
	228	* page_mapped_in_vma - check whether a page is really mapped in a VMA
	229	* @page: the page to test
	230	* @vma: the VMA to test
	231	*
	232	* Returns 1 if the page is mapped into the page tables of the VMA, 0
	233	* if the page is not mapped into the page tables of this VMA. Only
	234	* valid for normal file or anonymous VMAs.
	235	*/
	236	int page_mapped_in_vma(struct page page, struct vm_area_struct vma)
	237	{
	238	struct page_vma_mapped_walk pvmw = {
	239	.page = page,
	240	.vma = vma,
	241	.flags = PVMW_SYNC,
	242	};
	243	unsigned long start, end;
	244
	245	start = __vma_address(page, vma);
	246	end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
	247
	248	if (unlikely(end < vma->vm_start \|\| start >= vma->vm_end))
	249	return 0;
	250	pvmw.address = max(start, vma->vm_start);
	251	if (!page_vma_mapped_walk(&pvmw))
	252	return 0;
	253	page_vma_mapped_walk_done(&pvmw);
	254	return 1;
	255	}