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

#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 check_pmd(struct page_vma_mapped_walk *pvmw)
{
	pmd_t pmde;
	/*
	 * Make sure we don't re-load pmd between present and !trans_huge check.
	 * We need a consistent view.
	 */
	pmde = READ_ONCE(*pvmw->pmd);
	return pmd_present(pmde) && !pmd_trans_huge(pmde);
}

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 bool check_pte(struct page_vma_mapped_walk *pvmw)
{
	if (pvmw->flags & PVMW_MIGRATION) {
#ifdef CONFIG_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;
		if (migration_entry_to_page(entry) - pvmw->page >=
				hpage_nr_pages(pvmw->page)) {
			return false;
		}
		if (migration_entry_to_page(entry) < pvmw->page)
			return false;
#else
		WARN_ON_ONCE(1);
#endif
	} else {
		if (!pte_present(*pvmw->pte))
			return false;

		/* THP can be referenced by any subpage */
		if (pte_page(*pvmw->pte) - pvmw->page >=
				hpage_nr_pages(pvmw->page)) {
			return false;
		}
		if (pte_page(*pvmw->pte) < pvmw->page)
			return false;
	}

	return true;
}

/**
 * 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;

	/* 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);
	if (pmd_trans_huge(*pvmw->pmd) || is_pmd_migration_entry(*pvmw->pmd)) {
		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;
				}
			} else
				WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
			return not_found(pvmw);
		} else {
			/* THP pmd was split under us: handle on pte level */
			spin_unlock(pvmw->ptl);
			pvmw->ptl = NULL;
		}
	} else {
		if (!check_pmd(pvmw))
			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
ace71a19 KS	1	#include <linux/mm.h>
	2	#include <linux/rmap.h>
	3	#include <linux/hugetlb.h>
	4	#include <linux/swap.h>
	5	#include <linux/swapops.h>
	6
	7	#include "internal.h"
	8
	9	static inline bool check_pmd(struct page_vma_mapped_walk *pvmw)
	10	{
	11	pmd_t pmde;
	12	/*
	13	* Make sure we don't re-load pmd between present and !trans_huge check.
	14	* We need a consistent view.
	15	*/
	16	pmde = READ_ONCE(*pvmw->pmd);
	17	return pmd_present(pmde) && !pmd_trans_huge(pmde);
	18	}
	19
	20	static inline bool not_found(struct page_vma_mapped_walk *pvmw)
	21	{
	22	page_vma_mapped_walk_done(pvmw);
	23	return false;
	24	}
	25
	26	static bool map_pte(struct page_vma_mapped_walk *pvmw)
	27	{
	28	pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
	29	if (!(pvmw->flags & PVMW_SYNC)) {
	30	if (pvmw->flags & PVMW_MIGRATION) {
	31	if (!is_swap_pte(*pvmw->pte))
	32	return false;
	33	} else {
	34	if (!pte_present(*pvmw->pte))
	35	return false;
	36	}
	37	}
	38	pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
	39	spin_lock(pvmw->ptl);
	40	return true;
	41	}
	42
	43	static bool check_pte(struct page_vma_mapped_walk *pvmw)
	44	{
	45	if (pvmw->flags & PVMW_MIGRATION) {
	46	#ifdef CONFIG_MIGRATION
	47	swp_entry_t entry;
	48	if (!is_swap_pte(*pvmw->pte))
	49	return false;
	50	entry = pte_to_swp_entry(*pvmw->pte);
	51	if (!is_migration_entry(entry))
	52	return false;
	53	if (migration_entry_to_page(entry) - pvmw->page >=
	54	hpage_nr_pages(pvmw->page)) {
	55	return false;
	56	}
	57	if (migration_entry_to_page(entry) < pvmw->page)
	58	return false;
	59	#else
	60	WARN_ON_ONCE(1);
	61	#endif
	62	} else {
	63	if (!pte_present(*pvmw->pte))
	64	return false;
65
66	/* THP can be referenced by any subpage */
67	if (pte_page(*pvmw->pte) - pvmw->page >=
68	hpage_nr_pages(pvmw->page)) {
69	return false;
70	}
71	if (pte_page(*pvmw->pte) < pvmw->page)
72	return false;
73	}
74
75	return true;
76	}
77
78	/**
79	* page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at
80	* @pvmw->address
81	* @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
82	* must be set. pmd, pte and ptl must be NULL.
83	*
84	* Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
85	* to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
86	* adjusted if needed (for PTE-mapped THPs).
87	*
88	* If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
89	* (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
90	* a loop to find all PTEs that map the THP.
91	*
92	* For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
93	* regardless of which page table level the page is mapped at. @pvmw->pmd is
94	* NULL.
95	*
96	* Retruns false if there are no more page table entries for the page in
97	* the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
98	*
99	* If you need to stop the walk before page_vma_mapped_walk() returned false,
100	* use page_vma_mapped_walk_done(). It will do the housekeeping.
101	*/
102	bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
103	{
104	struct mm_struct *mm = pvmw->vma->vm_mm;
105	struct page *page = pvmw->page;
106	pgd_t *pgd;
c2febafc	107	p4d_t *p4d;
ace71a19 KS	108	pud_t *pud;
	109
	110	/* The only possible pmd mapping has been handled on last iteration */
	111	if (pvmw->pmd && !pvmw->pte)
	112	return not_found(pvmw);
	113
d75450ff	114	if (pvmw->pte)
ace71a19	115	goto next_pte;
ace71a19 KS	116
	117	if (unlikely(PageHuge(pvmw->page))) {
	118	/* when pud is not present, pte will be NULL */
7868a208 PA	119	pvmw->pte = huge_pte_offset(mm, pvmw->address,
7868a208 PA	120	PAGE_SIZE << compound_order(page));
ace71a19 KS	121	if (!pvmw->pte)
	122	return false;
	123
	124	pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
	125	spin_lock(pvmw->ptl);
	126	if (!check_pte(pvmw))
	127	return not_found(pvmw);
	128	return true;
	129	}
	130	restart:
	131	pgd = pgd_offset(mm, pvmw->address);
	132	if (!pgd_present(*pgd))
	133	return false;
c2febafc KS	134	p4d = p4d_offset(pgd, pvmw->address);
	135	if (!p4d_present(*p4d))
	136	return false;
	137	pud = pud_offset(p4d, pvmw->address);
ace71a19 KS	138	if (!pud_present(*pud))
	139	return false;
	140	pvmw->pmd = pmd_offset(pud, pvmw->address);
616b8371	141	if (pmd_trans_huge(pvmw->pmd) \|\| is_pmd_migration_entry(pvmw->pmd)) {
ace71a19	142	pvmw->ptl = pmd_lock(mm, pvmw->pmd);
ace71a19 KS	143	if (likely(pmd_trans_huge(*pvmw->pmd))) {
	144	if (pvmw->flags & PVMW_MIGRATION)
	145	return not_found(pvmw);
	146	if (pmd_page(*pvmw->pmd) != page)
	147	return not_found(pvmw);
	148	return true;
616b8371 ZY	149	} else if (!pmd_present(*pvmw->pmd)) {
	150	if (thp_migration_supported()) {
	151	if (!(pvmw->flags & PVMW_MIGRATION))
	152	return not_found(pvmw);
	153	if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) {
	154	swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd);
	155
	156	if (migration_entry_to_page(entry) != page)
	157	return not_found(pvmw);
	158	return true;
	159	}
	160	} else
	161	WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
	162	return not_found(pvmw);
ace71a19 KS	163	} else {
	164	/* THP pmd was split under us: handle on pte level */
	165	spin_unlock(pvmw->ptl);
	166	pvmw->ptl = NULL;
	167	}
	168	} else {
	169	if (!check_pmd(pvmw))
	170	return false;
	171	}
	172	if (!map_pte(pvmw))
	173	goto next_pte;
	174	while (1) {
	175	if (check_pte(pvmw))
	176	return true;
d75450ff HD	177	next_pte:
	178	/* Seek to next pte only makes sense for THP */
	179	if (!PageTransHuge(pvmw->page) \|\| PageHuge(pvmw->page))
	180	return not_found(pvmw);
	181	do {
ace71a19	182	pvmw->address += PAGE_SIZE;
d75450ff HD	183	if (pvmw->address >= pvmw->vma->vm_end \|\|
d75450ff HD	184	pvmw->address >=
ace71a19 KS	185	__vma_address(pvmw->page, pvmw->vma) +
	186	hpage_nr_pages(pvmw->page) * PAGE_SIZE)
	187	return not_found(pvmw);
	188	/* Did we cross page table boundary? */
	189	if (pvmw->address % PMD_SIZE == 0) {
	190	pte_unmap(pvmw->pte);
	191	if (pvmw->ptl) {
	192	spin_unlock(pvmw->ptl);
	193	pvmw->ptl = NULL;
	194	}
	195	goto restart;
	196	} else {
	197	pvmw->pte++;
	198	}
	199	} while (pte_none(*pvmw->pte));
	200
	201	if (!pvmw->ptl) {
	202	pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
	203	spin_lock(pvmw->ptl);
	204	}
	205	}
	206	}
6a328a62 KS	207
	208	/**
	209	* page_mapped_in_vma - check whether a page is really mapped in a VMA
	210	* @page: the page to test
	211	* @vma: the VMA to test
	212	*
	213	* Returns 1 if the page is mapped into the page tables of the VMA, 0
	214	* if the page is not mapped into the page tables of this VMA. Only
	215	* valid for normal file or anonymous VMAs.
	216	*/
	217	int page_mapped_in_vma(struct page page, struct vm_area_struct vma)
	218	{
	219	struct page_vma_mapped_walk pvmw = {
	220	.page = page,
	221	.vma = vma,
	222	.flags = PVMW_SYNC,
	223	};
	224	unsigned long start, end;
	225
	226	start = __vma_address(page, vma);
	227	end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
	228
	229	if (unlikely(end < vma->vm_start \|\| start >= vma->vm_end))
	230	return 0;
	231	pvmw.address = max(start, vma->vm_start);
	232	if (!page_vma_mapped_walk(&pvmw))
	233	return 0;
	234	page_vma_mapped_walk_done(&pvmw);
	235	return 1;
	236	}