[mirror_ubuntu-bionic-kernel.git] / arch / x86 / mm / gup.c

/*
 * Lockless get_user_pages_fast for x86
 *
 * Copyright (C) 2008 Nick Piggin
 * Copyright (C) 2008 Novell Inc.
 */
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/vmstat.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/memremap.h>

#include <asm/mmu_context.h>
#include <asm/pgtable.h>

static inline pte_t gup_get_pte(pte_t *ptep)
{
#ifndef CONFIG_X86_PAE
	return READ_ONCE(*ptep);
#else
	/*
	 * With get_user_pages_fast, we walk down the pagetables without taking
	 * any locks.  For this we would like to load the pointers atomically,
	 * but that is not possible (without expensive cmpxchg8b) on PAE.  What
	 * we do have is the guarantee that a pte will only either go from not
	 * present to present, or present to not present or both -- it will not
	 * switch to a completely different present page without a TLB flush in
	 * between; something that we are blocking by holding interrupts off.
	 *
	 * Setting ptes from not present to present goes:
	 * ptep->pte_high = h;
	 * smp_wmb();
	 * ptep->pte_low = l;
	 *
	 * And present to not present goes:
	 * ptep->pte_low = 0;
	 * smp_wmb();
	 * ptep->pte_high = 0;
	 *
	 * We must ensure here that the load of pte_low sees l iff pte_high
	 * sees h. We load pte_high *after* loading pte_low, which ensures we
	 * don't see an older value of pte_high.  *Then* we recheck pte_low,
	 * which ensures that we haven't picked up a changed pte high. We might
	 * have got rubbish values from pte_low and pte_high, but we are
	 * guaranteed that pte_low will not have the present bit set *unless*
	 * it is 'l'. And get_user_pages_fast only operates on present ptes, so
	 * we're safe.
	 *
	 * gup_get_pte should not be used or copied outside gup.c without being
	 * very careful -- it does not atomically load the pte or anything that
	 * is likely to be useful for you.
	 */
	pte_t pte;

retry:
	pte.pte_low = ptep->pte_low;
	smp_rmb();
	pte.pte_high = ptep->pte_high;
	smp_rmb();
	if (unlikely(pte.pte_low != ptep->pte_low))
		goto retry;

	return pte;
#endif
}

static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
{
	while ((*nr) - nr_start) {
		struct page *page = pages[--(*nr)];

		ClearPageReferenced(page);
		put_page(page);
	}
}

/*
 * 'pteval' can come from a pte, pmd or pud.  We only check
 * _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
 * same value on all 3 types.
 */
static inline int pte_allows_gup(unsigned long pteval, int write)
{
	unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;

	if (write)
		need_pte_bits |= _PAGE_RW;

	if ((pteval & need_pte_bits) != need_pte_bits)
		return 0;

	/* Check memory protection keys permissions. */
	if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
		return 0;

	return 1;
}

/*
 * The performance critical leaf functions are made noinline otherwise gcc
 * inlines everything into a single function which results in too much
 * register pressure.
 */
static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
	struct dev_pagemap *pgmap = NULL;
	int nr_start = *nr, ret = 0;
	pte_t *ptep, *ptem;

	/*
	 * Keep the original mapped PTE value (ptem) around since we
	 * might increment ptep off the end of the page when finishing
	 * our loop iteration.
	 */
	ptem = ptep = pte_offset_map(&pmd, addr);
	do {
		pte_t pte = gup_get_pte(ptep);
		struct page *page;

		/* Similar to the PMD case, NUMA hinting must take slow path */
		if (pte_protnone(pte))
			break;

		if (!pte_allows_gup(pte_val(pte), write))
			break;

		if (pte_devmap(pte)) {
			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
			if (unlikely(!pgmap)) {
				undo_dev_pagemap(nr, nr_start, pages);
				break;
			}
		} else if (pte_special(pte))
			break;

		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
		page = pte_page(pte);
		get_page(page);
		put_dev_pagemap(pgmap);
		SetPageReferenced(page);
		pages[*nr] = page;
		(*nr)++;

	} while (ptep++, addr += PAGE_SIZE, addr != end);
	if (addr == end)
		ret = 1;
	pte_unmap(ptem);

	return ret;
}

static inline void get_head_page_multiple(struct page *page, int nr)
{
	VM_BUG_ON_PAGE(page != compound_head(page), page);
	VM_BUG_ON_PAGE(page_count(page) == 0, page);
	page_ref_add(page, nr);
	SetPageReferenced(page);
}

static int __gup_device_huge(unsigned long pfn, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	int nr_start = *nr;
	struct dev_pagemap *pgmap = NULL;

	do {
		struct page *page = pfn_to_page(pfn);

		pgmap = get_dev_pagemap(pfn, pgmap);
		if (unlikely(!pgmap)) {
			undo_dev_pagemap(nr, nr_start, pages);
			return 0;
		}
		SetPageReferenced(page);
		pages[*nr] = page;
		get_page(page);
		put_dev_pagemap(pgmap);
		(*nr)++;
		pfn++;
	} while (addr += PAGE_SIZE, addr != end);
	return 1;
}

static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;

	fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
}

static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;

	fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
}

static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
	struct page *head, *page;
	int refs;

	if (!pte_allows_gup(pmd_val(pmd), write))
		return 0;

	VM_BUG_ON(!pfn_valid(pmd_pfn(pmd)));
	if (pmd_devmap(pmd))
		return __gup_device_huge_pmd(pmd, addr, end, pages, nr);

	/* hugepages are never "special" */
	VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);

	refs = 0;
	head = pmd_page(pmd);
	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	do {
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);
	get_head_page_multiple(head, refs);

	return 1;
}

static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
		int write, struct page **pages, int *nr)
{
	unsigned long next;
	pmd_t *pmdp;

	pmdp = pmd_offset(&pud, addr);
	do {
		pmd_t pmd = *pmdp;

		next = pmd_addr_end(addr, end);
		if (pmd_none(pmd))
			return 0;
		if (unlikely(pmd_large(pmd) || !pmd_present(pmd))) {
			/*
			 * NUMA hinting faults need to be handled in the GUP
			 * slowpath for accounting purposes and so that they
			 * can be serialised against THP migration.
			 */
			if (pmd_protnone(pmd))
				return 0;
			if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
				return 0;
		} else {
			if (!gup_pte_range(pmd, addr, next, write, pages, nr))
				return 0;
		}
	} while (pmdp++, addr = next, addr != end);

	return 1;
}

static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
	struct page *head, *page;
	int refs;

	if (!pte_allows_gup(pud_val(pud), write))
		return 0;

	VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
	if (pud_devmap(pud))
		return __gup_device_huge_pud(pud, addr, end, pages, nr);

	/* hugepages are never "special" */
	VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);

	refs = 0;
	head = pud_page(pud);
	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	do {
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
	} while (addr += PAGE_SIZE, addr != end);
	get_head_page_multiple(head, refs);

	return 1;
}

static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
			int write, struct page **pages, int *nr)
{
	unsigned long next;
	pud_t *pudp;

	pudp = pud_offset(&pgd, addr);
	do {
		pud_t pud = *pudp;

		next = pud_addr_end(addr, end);
		if (pud_none(pud))
			return 0;
		if (unlikely(pud_large(pud))) {
			if (!gup_huge_pud(pud, addr, next, write, pages, nr))
				return 0;
		} else {
			if (!gup_pmd_range(pud, addr, next, write, pages, nr))
				return 0;
		}
	} while (pudp++, addr = next, addr != end);

	return 1;
}

/*
 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 * back to the regular GUP.
 */
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
			  struct page **pages)
{
	struct mm_struct *mm = current->mm;
	unsigned long addr, len, end;
	unsigned long next;
	unsigned long flags;
	pgd_t *pgdp;
	int nr = 0;

	start &= PAGE_MASK;
	addr = start;
	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;
	if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
					(void __user *)start, len)))
		return 0;

	/*
	 * XXX: batch / limit 'nr', to avoid large irq off latency
	 * needs some instrumenting to determine the common sizes used by
	 * important workloads (eg. DB2), and whether limiting the batch size
	 * will decrease performance.
	 *
	 * It seems like we're in the clear for the moment. Direct-IO is
	 * the main guy that batches up lots of get_user_pages, and even
	 * they are limited to 64-at-a-time which is not so many.
	 */
	/*
	 * This doesn't prevent pagetable teardown, but does prevent
	 * the pagetables and pages from being freed on x86.
	 *
	 * So long as we atomically load page table pointers versus teardown
	 * (which we do on x86, with the above PAE exception), we can follow the
	 * address down to the the page and take a ref on it.
	 */
	local_irq_save(flags);
	pgdp = pgd_offset(mm, addr);
	do {
		pgd_t pgd = *pgdp;

		next = pgd_addr_end(addr, end);
		if (pgd_none(pgd))
			break;
		if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
			break;
	} while (pgdp++, addr = next, addr != end);
	local_irq_restore(flags);

	return nr;
}

/**
 * get_user_pages_fast() - pin user pages in memory
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @write:	whether pages will be written to
 * @pages:	array that receives pointers to the pages pinned.
 * 		Should be at least nr_pages long.
 *
 * Attempt to pin user pages in memory without taking mm->mmap_sem.
 * If not successful, it will fall back to taking the lock and
 * calling get_user_pages().
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno.
 */
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
			struct page **pages)
{
	struct mm_struct *mm = current->mm;
	unsigned long addr, len, end;
	unsigned long next;
	pgd_t *pgdp;
	int nr = 0;

	start &= PAGE_MASK;
	addr = start;
	len = (unsigned long) nr_pages << PAGE_SHIFT;

	end = start + len;
	if (end < start)
		goto slow_irqon;

#ifdef CONFIG_X86_64
	if (end >> __VIRTUAL_MASK_SHIFT)
		goto slow_irqon;
#endif

	/*
	 * XXX: batch / limit 'nr', to avoid large irq off latency
	 * needs some instrumenting to determine the common sizes used by
	 * important workloads (eg. DB2), and whether limiting the batch size
	 * will decrease performance.
	 *
	 * It seems like we're in the clear for the moment. Direct-IO is
	 * the main guy that batches up lots of get_user_pages, and even
	 * they are limited to 64-at-a-time which is not so many.
	 */
	/*
	 * This doesn't prevent pagetable teardown, but does prevent
	 * the pagetables and pages from being freed on x86.
	 *
	 * So long as we atomically load page table pointers versus teardown
	 * (which we do on x86, with the above PAE exception), we can follow the
	 * address down to the the page and take a ref on it.
	 */
	local_irq_disable();
	pgdp = pgd_offset(mm, addr);
	do {
		pgd_t pgd = *pgdp;

		next = pgd_addr_end(addr, end);
		if (pgd_none(pgd))
			goto slow;
		if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
			goto slow;
	} while (pgdp++, addr = next, addr != end);
	local_irq_enable();

	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
	return nr;

	{
		int ret;

slow:
		local_irq_enable();
slow_irqon:
		/* Try to get the remaining pages with get_user_pages */
		start += nr << PAGE_SHIFT;
		pages += nr;

		ret = get_user_pages_unlocked(start,
					      (end - start) >> PAGE_SHIFT,
					      pages, write ? FOLL_WRITE : 0);

		/* Have to be a bit careful with return values */
		if (nr > 0) {
			if (ret < 0)
				ret = nr;
			else
				ret += nr;
		}

		return ret;
	}
}
Commit	Line	Data
8174c430 NP	1	/*
	2	* Lockless get_user_pages_fast for x86
	3	*
	4	* Copyright (C) 2008 Nick Piggin
	5	* Copyright (C) 2008 Novell Inc.
	6	*/
	7	#include <linux/sched.h>
	8	#include <linux/mm.h>
	9	#include <linux/vmstat.h>
	10	#include <linux/highmem.h>
8ee53820	11	#include <linux/swap.h>
3565fce3	12	#include <linux/memremap.h>
8174c430	13
33a709b2	14	#include <asm/mmu_context.h>
8174c430 NP	15	#include <asm/pgtable.h>
	16
	17	static inline pte_t gup_get_pte(pte_t *ptep)
	18	{
	19	#ifndef CONFIG_X86_PAE
14cf3d97	20	return READ_ONCE(*ptep);
8174c430 NP	21	#else
	22	/*
	23	* With get_user_pages_fast, we walk down the pagetables without taking
ab09809f	24	* any locks. For this we would like to load the pointers atomically,
8174c430 NP	25	* but that is not possible (without expensive cmpxchg8b) on PAE. What
	26	* we do have is the guarantee that a pte will only either go from not
	27	* present to present, or present to not present or both -- it will not
	28	* switch to a completely different present page without a TLB flush in
	29	* between; something that we are blocking by holding interrupts off.
	30	*
	31	* Setting ptes from not present to present goes:
	32	* ptep->pte_high = h;
	33	* smp_wmb();
	34	* ptep->pte_low = l;
	35	*
	36	* And present to not present goes:
	37	* ptep->pte_low = 0;
	38	* smp_wmb();
	39	* ptep->pte_high = 0;
	40	*
	41	* We must ensure here that the load of pte_low sees l iff pte_high
	42	* sees h. We load pte_high after loading pte_low, which ensures we
	43	* don't see an older value of pte_high. Then we recheck pte_low,
	44	* which ensures that we haven't picked up a changed pte high. We might
	45	* have got rubbish values from pte_low and pte_high, but we are
	46	* guaranteed that pte_low will not have the present bit set unless
	47	* it is 'l'. And get_user_pages_fast only operates on present ptes, so
	48	* we're safe.
	49	*
	50	* gup_get_pte should not be used or copied outside gup.c without being
	51	* very careful -- it does not atomically load the pte or anything that
	52	* is likely to be useful for you.
	53	*/
	54	pte_t pte;
	55
	56	retry:
	57	pte.pte_low = ptep->pte_low;
	58	smp_rmb();
	59	pte.pte_high = ptep->pte_high;
	60	smp_rmb();
	61	if (unlikely(pte.pte_low != ptep->pte_low))
	62	goto retry;
	63
	64	return pte;
	65	#endif
	66	}
	67
3565fce3 DW	68	static void undo_dev_pagemap(int nr, int nr_start, struct page *pages)
	69	{
	70	while ((*nr) - nr_start) {
	71	struct page page = pages[--(nr)];
	72
	73	ClearPageReferenced(page);
	74	put_page(page);
	75	}
	76	}
	77
1874f689 DH	78	/*
	79	* 'pteval' can come from a pte, pmd or pud. We only check
	80	* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
	81	* same value on all 3 types.
	82	*/
	83	static inline int pte_allows_gup(unsigned long pteval, int write)
	84	{
	85	unsigned long need_pte_bits = _PAGE_PRESENT\|_PAGE_USER;
	86
	87	if (write)
	88	need_pte_bits \|= _PAGE_RW;
	89
	90	if ((pteval & need_pte_bits) != need_pte_bits)
	91	return 0;
	92
33a709b2 DH	93	/* Check memory protection keys permissions. */
	94	if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
	95	return 0;
	96
1874f689 DH	97	return 1;
	98	}
	99
8174c430 NP	100	/*
	101	* The performance critical leaf functions are made noinline otherwise gcc
	102	* inlines everything into a single function which results in too much
	103	* register pressure.
	104	*/
	105	static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
	106	unsigned long end, int write, struct page *pages, int nr)
	107	{
3565fce3	108	struct dev_pagemap *pgmap = NULL;
b2e593e2 DW	109	int nr_start = *nr, ret = 0;
b2e593e2 DW	110	pte_t ptep, ptem;
8174c430	111
b2e593e2 DW	112	/*
	113	* Keep the original mapped PTE value (ptem) around since we
	114	* might increment ptep off the end of the page when finishing
	115	* our loop iteration.
	116	*/
	117	ptem = ptep = pte_offset_map(&pmd, addr);
8174c430 NP	118	do {
	119	pte_t pte = gup_get_pte(ptep);
	120	struct page *page;
	121
2b4847e7	122	/* Similar to the PMD case, NUMA hinting must take slow path */
b2e593e2 DW	123	if (pte_protnone(pte))
b2e593e2 DW	124	break;
2b4847e7	125
b2e593e2 DW	126	if (!pte_allows_gup(pte_val(pte), write))
b2e593e2 DW	127	break;
ef947b25	128
3565fce3 DW	129	if (pte_devmap(pte)) {
	130	pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
	131	if (unlikely(!pgmap)) {
	132	undo_dev_pagemap(nr, nr_start, pages);
b2e593e2	133	break;
3565fce3	134	}
b2e593e2 DW	135	} else if (pte_special(pte))
	136	break;
	137
8174c430	138	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
457a98b0	139	page = pte_page(pte);
8174c430	140	get_page(page);
3565fce3	141	put_dev_pagemap(pgmap);
8ee53820	142	SetPageReferenced(page);
8174c430 NP	143	pages[*nr] = page;
	144	(*nr)++;
	145
	146	} while (ptep++, addr += PAGE_SIZE, addr != end);
b2e593e2 DW	147	if (addr == end)
	148	ret = 1;
	149	pte_unmap(ptem);
8174c430	150
b2e593e2	151	return ret;
8174c430 NP	152	}
	153
	154	static inline void get_head_page_multiple(struct page *page, int nr)
	155	{
309381fe SL	156	VM_BUG_ON_PAGE(page != compound_head(page), page);
309381fe SL	157	VM_BUG_ON_PAGE(page_count(page) == 0, page);
fe896d18	158	page_ref_add(page, nr);
8ee53820	159	SetPageReferenced(page);
8174c430 NP	160	}
8174c430 NP	161
220ced16	162	static int __gup_device_huge(unsigned long pfn, unsigned long addr,
3565fce3 DW	163	unsigned long end, struct page *pages, int nr)
	164	{
	165	int nr_start = *nr;
3565fce3 DW	166	struct dev_pagemap *pgmap = NULL;
3565fce3 DW	167
3565fce3 DW	168	do {
	169	struct page *page = pfn_to_page(pfn);
	170
	171	pgmap = get_dev_pagemap(pfn, pgmap);
	172	if (unlikely(!pgmap)) {
	173	undo_dev_pagemap(nr, nr_start, pages);
	174	return 0;
	175	}
	176	SetPageReferenced(page);
	177	pages[*nr] = page;
	178	get_page(page);
	179	put_dev_pagemap(pgmap);
	180	(*nr)++;
	181	pfn++;
	182	} while (addr += PAGE_SIZE, addr != end);
	183	return 1;
	184	}
	185
220ced16 DW	186	static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
	187	unsigned long end, struct page *pages, int nr)
	188	{
	189	unsigned long fault_pfn;
	190
	191	fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	192	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
	193	}
	194
	195	static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
	196	unsigned long end, struct page *pages, int nr)
	197	{
	198	unsigned long fault_pfn;
	199
	200	fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	201	return __gup_device_huge(fault_pfn, addr, end, pages, nr);
	202	}
	203
8174c430 NP	204	static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
	205	unsigned long end, int write, struct page *pages, int nr)
	206	{
8174c430 NP	207	struct page head, page;
	208	int refs;
	209
1874f689	210	if (!pte_allows_gup(pmd_val(pmd), write))
8174c430	211	return 0;
3565fce3 DW	212
	213	VM_BUG_ON(!pfn_valid(pmd_pfn(pmd)));
	214	if (pmd_devmap(pmd))
	215	return __gup_device_huge_pmd(pmd, addr, end, pages, nr);
	216
8174c430	217	/* hugepages are never "special" */
daf3e35c	218	VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);
8174c430 NP	219
8174c430 NP	220	refs = 0;
daf3e35c	221	head = pmd_page(pmd);
652ea695	222	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
8174c430	223	do {
309381fe	224	VM_BUG_ON_PAGE(compound_head(page) != head, page);
8174c430 NP	225	pages[*nr] = page;
	226	(*nr)++;
	227	page++;
	228	refs++;
	229	} while (addr += PAGE_SIZE, addr != end);
	230	get_head_page_multiple(head, refs);
	231
	232	return 1;
	233	}
	234
	235	static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
	236	int write, struct page *pages, int nr)
	237	{
	238	unsigned long next;
	239	pmd_t *pmdp;
	240
	241	pmdp = pmd_offset(&pud, addr);
	242	do {
	243	pmd_t pmd = *pmdp;
	244
	245	next = pmd_addr_end(addr, end);
1f19617d	246	if (pmd_none(pmd))
8174c430	247	return 0;
cbef8478	248	if (unlikely(pmd_large(pmd) \|\| !pmd_present(pmd))) {
2b4847e7 MG	249	/*
	250	* NUMA hinting faults need to be handled in the GUP
	251	* slowpath for accounting purposes and so that they
	252	* can be serialised against THP migration.
	253	*/
8a0516ed	254	if (pmd_protnone(pmd))
2b4847e7	255	return 0;
8174c430 NP	256	if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
	257	return 0;
	258	} else {
	259	if (!gup_pte_range(pmd, addr, next, write, pages, nr))
	260	return 0;
	261	}
	262	} while (pmdp++, addr = next, addr != end);
	263
	264	return 1;
	265	}
	266
652ea695 NP	267	static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
	268	unsigned long end, int write, struct page *pages, int nr)
	269	{
652ea695 NP	270	struct page head, page;
	271	int refs;
	272
1874f689	273	if (!pte_allows_gup(pud_val(pud), write))
652ea695	274	return 0;
220ced16 DW	275
	276	VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
	277	if (pud_devmap(pud))
	278	return __gup_device_huge_pud(pud, addr, end, pages, nr);
	279
652ea695	280	/* hugepages are never "special" */
daf3e35c	281	VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
652ea695 NP	282
652ea695 NP	283	refs = 0;
daf3e35c	284	head = pud_page(pud);
652ea695 NP	285	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
652ea695 NP	286	do {
309381fe	287	VM_BUG_ON_PAGE(compound_head(page) != head, page);
652ea695 NP	288	pages[*nr] = page;
	289	(*nr)++;
	290	page++;
	291	refs++;
	292	} while (addr += PAGE_SIZE, addr != end);
	293	get_head_page_multiple(head, refs);
	294
	295	return 1;
	296	}
	297
8174c430 NP	298	static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
	299	int write, struct page *pages, int nr)
	300	{
	301	unsigned long next;
	302	pud_t *pudp;
	303
	304	pudp = pud_offset(&pgd, addr);
	305	do {
	306	pud_t pud = *pudp;
	307
	308	next = pud_addr_end(addr, end);
	309	if (pud_none(pud))
	310	return 0;
652ea695 NP	311	if (unlikely(pud_large(pud))) {
	312	if (!gup_huge_pud(pud, addr, next, write, pages, nr))
	313	return 0;
	314	} else {
	315	if (!gup_pmd_range(pud, addr, next, write, pages, nr))
	316	return 0;
	317	}
8174c430 NP	318	} while (pudp++, addr = next, addr != end);
	319
	320	return 1;
	321	}
	322
465a454f PZ	323	/*
	324	* Like get_user_pages_fast() except its IRQ-safe in that it won't fall
	325	* back to the regular GUP.
	326	*/
	327	int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
	328	struct page **pages)
	329	{
	330	struct mm_struct *mm = current->mm;
	331	unsigned long addr, len, end;
	332	unsigned long next;
	333	unsigned long flags;
	334	pgd_t *pgdp;
	335	int nr = 0;
	336
	337	start &= PAGE_MASK;
	338	addr = start;
	339	len = (unsigned long) nr_pages << PAGE_SHIFT;
	340	end = start + len;
	341	if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
	342	(void __user *)start, len)))
	343	return 0;
	344
	345	/*
	346	* XXX: batch / limit 'nr', to avoid large irq off latency
	347	* needs some instrumenting to determine the common sizes used by
	348	* important workloads (eg. DB2), and whether limiting the batch size
	349	* will decrease performance.
	350	*
	351	* It seems like we're in the clear for the moment. Direct-IO is
	352	* the main guy that batches up lots of get_user_pages, and even
	353	* they are limited to 64-at-a-time which is not so many.
	354	*/
	355	/*
	356	* This doesn't prevent pagetable teardown, but does prevent
	357	* the pagetables and pages from being freed on x86.
	358	*
	359	* So long as we atomically load page table pointers versus teardown
	360	* (which we do on x86, with the above PAE exception), we can follow the
	361	* address down to the the page and take a ref on it.
	362	*/
	363	local_irq_save(flags);
	364	pgdp = pgd_offset(mm, addr);
	365	do {
	366	pgd_t pgd = *pgdp;
	367
	368	next = pgd_addr_end(addr, end);
	369	if (pgd_none(pgd))
	370	break;
	371	if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
	372	break;
	373	} while (pgdp++, addr = next, addr != end);
	374	local_irq_restore(flags);
	375
	376	return nr;
	377	}
	378
a0d22f48 AG	379	/**
	380	* get_user_pages_fast() - pin user pages in memory
	381	* @start: starting user address
	382	* @nr_pages: number of pages from start to pin
	383	* @write: whether pages will be written to
	384	* @pages: array that receives pointers to the pages pinned.
	385	* Should be at least nr_pages long.
	386	*
	387	* Attempt to pin user pages in memory without taking mm->mmap_sem.
	388	* If not successful, it will fall back to taking the lock and
	389	* calling get_user_pages().
	390	*
	391	* Returns number of pages pinned. This may be fewer than the number
	392	* requested. If nr_pages is 0 or negative, returns 0. If no pages
	393	* were pinned, returns -errno.
	394	*/
8174c430 NP	395	int get_user_pages_fast(unsigned long start, int nr_pages, int write,
	396	struct page **pages)
	397	{
	398	struct mm_struct *mm = current->mm;
9b79022c	399	unsigned long addr, len, end;
8174c430 NP	400	unsigned long next;
	401	pgd_t *pgdp;
	402	int nr = 0;
	403
9b79022c LT	404	start &= PAGE_MASK;
	405	addr = start;
	406	len = (unsigned long) nr_pages << PAGE_SHIFT;
7f818906	407
9b79022c	408	end = start + len;
7f818906 LT	409	if (end < start)
	410	goto slow_irqon;
	411
	412	#ifdef CONFIG_X86_64
	413	if (end >> __VIRTUAL_MASK_SHIFT)
8174c430	414	goto slow_irqon;
7f818906	415	#endif
8174c430 NP	416
	417	/*
	418	* XXX: batch / limit 'nr', to avoid large irq off latency
	419	* needs some instrumenting to determine the common sizes used by
	420	* important workloads (eg. DB2), and whether limiting the batch size
	421	* will decrease performance.
	422	*
	423	* It seems like we're in the clear for the moment. Direct-IO is
	424	* the main guy that batches up lots of get_user_pages, and even
	425	* they are limited to 64-at-a-time which is not so many.
	426	*/
	427	/*
	428	* This doesn't prevent pagetable teardown, but does prevent
	429	* the pagetables and pages from being freed on x86.
	430	*
	431	* So long as we atomically load page table pointers versus teardown
	432	* (which we do on x86, with the above PAE exception), we can follow the
	433	* address down to the the page and take a ref on it.
	434	*/
	435	local_irq_disable();
	436	pgdp = pgd_offset(mm, addr);
	437	do {
	438	pgd_t pgd = *pgdp;
	439
	440	next = pgd_addr_end(addr, end);
	441	if (pgd_none(pgd))
	442	goto slow;
	443	if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
	444	goto slow;
	445	} while (pgdp++, addr = next, addr != end);
	446	local_irq_enable();
	447
	448	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
	449	return nr;
	450
	451	{
	452	int ret;
	453
	454	slow:
	455	local_irq_enable();
	456	slow_irqon:
	457	/* Try to get the remaining pages with get_user_pages */
	458	start += nr << PAGE_SHIFT;
	459	pages += nr;
	460
d4edcf0d	461	ret = get_user_pages_unlocked(start,
a7b78075	462	(end - start) >> PAGE_SHIFT,
c164154f	463	pages, write ? FOLL_WRITE : 0);
8174c430 NP	464
	465	/* Have to be a bit careful with return values */
	466	if (nr > 0) {
	467	if (ret < 0)
	468	ret = nr;
	469	else
	470	ret += nr;
	471	}
	472
	473	return ret;
	474	}
	475	}