gup.c 70.9 KB
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// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/spinlock.h>

#include <linux/mm.h>
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#include <linux/memremap.h>
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#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>

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#include <linux/sched/signal.h>
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#include <linux/rwsem.h>
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#include <linux/hugetlb.h>
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#include <linux/migrate.h>
#include <linux/mm_inline.h>
#include <linux/sched/mm.h>
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#include <asm/mmu_context.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include "internal.h"

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struct follow_page_context {
	struct dev_pagemap *pgmap;
	unsigned int page_mask;
};

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/*
 * Return the compound head page with ref appropriately incremented,
 * or NULL if that failed.
 */
static inline struct page *try_get_compound_head(struct page *page, int refs)
{
	struct page *head = compound_head(page);

	if (WARN_ON_ONCE(page_ref_count(head) < 0))
		return NULL;
	if (unlikely(!page_cache_add_speculative(head, refs)))
		return NULL;
	return head;
}

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/**
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 * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
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 * @pages:  array of pages to be maybe marked dirty, and definitely released.
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 * @npages: number of pages in the @pages array.
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 * @make_dirty: whether to mark the pages dirty
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 *
 * "gup-pinned page" refers to a page that has had one of the get_user_pages()
 * variants called on that page.
 *
 * For each page in the @pages array, make that page (or its head page, if a
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 * compound page) dirty, if @make_dirty is true, and if the page was previously
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 * listed as clean. In any case, releases all pages using unpin_user_page(),
 * possibly via unpin_user_pages(), for the non-dirty case.
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 *
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 * Please see the unpin_user_page() documentation for details.
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 *
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 * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is
 * required, then the caller should a) verify that this is really correct,
 * because _lock() is usually required, and b) hand code it:
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 * set_page_dirty_lock(), unpin_user_page().
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 *
 */
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void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
				 bool make_dirty)
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{
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	unsigned long index;
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	/*
	 * TODO: this can be optimized for huge pages: if a series of pages is
	 * physically contiguous and part of the same compound page, then a
	 * single operation to the head page should suffice.
	 */

	if (!make_dirty) {
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		unpin_user_pages(pages, npages);
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		return;
	}

	for (index = 0; index < npages; index++) {
		struct page *page = compound_head(pages[index]);
		/*
		 * Checking PageDirty at this point may race with
		 * clear_page_dirty_for_io(), but that's OK. Two key
		 * cases:
		 *
		 * 1) This code sees the page as already dirty, so it
		 * skips the call to set_page_dirty(). That could happen
		 * because clear_page_dirty_for_io() called
		 * page_mkclean(), followed by set_page_dirty().
		 * However, now the page is going to get written back,
		 * which meets the original intention of setting it
		 * dirty, so all is well: clear_page_dirty_for_io() goes
		 * on to call TestClearPageDirty(), and write the page
		 * back.
		 *
		 * 2) This code sees the page as clean, so it calls
		 * set_page_dirty(). The page stays dirty, despite being
		 * written back, so it gets written back again in the
		 * next writeback cycle. This is harmless.
		 */
		if (!PageDirty(page))
			set_page_dirty_lock(page);
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		unpin_user_page(page);
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	}
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}
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EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
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/**
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 * unpin_user_pages() - release an array of gup-pinned pages.
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 * @pages:  array of pages to be marked dirty and released.
 * @npages: number of pages in the @pages array.
 *
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 * For each page in the @pages array, release the page using unpin_user_page().
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 *
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 * Please see the unpin_user_page() documentation for details.
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 */
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void unpin_user_pages(struct page **pages, unsigned long npages)
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{
	unsigned long index;

	/*
	 * TODO: this can be optimized for huge pages: if a series of pages is
	 * physically contiguous and part of the same compound page, then a
	 * single operation to the head page should suffice.
	 */
	for (index = 0; index < npages; index++)
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		unpin_user_page(pages[index]);
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}
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EXPORT_SYMBOL(unpin_user_pages);
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#ifdef CONFIG_MMU
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static struct page *no_page_table(struct vm_area_struct *vma,
		unsigned int flags)
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{
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	/*
	 * When core dumping an enormous anonymous area that nobody
	 * has touched so far, we don't want to allocate unnecessary pages or
	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
	 * then get_dump_page() will return NULL to leave a hole in the dump.
	 * But we can only make this optimization where a hole would surely
	 * be zero-filled if handle_mm_fault() actually did handle it.
	 */
	if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault))
		return ERR_PTR(-EFAULT);
	return NULL;
}
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static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
		pte_t *pte, unsigned int flags)
{
	/* No page to get reference */
	if (flags & FOLL_GET)
		return -EFAULT;

	if (flags & FOLL_TOUCH) {
		pte_t entry = *pte;

		if (flags & FOLL_WRITE)
			entry = pte_mkdirty(entry);
		entry = pte_mkyoung(entry);

		if (!pte_same(*pte, entry)) {
			set_pte_at(vma->vm_mm, address, pte, entry);
			update_mmu_cache(vma, address, pte);
		}
	}

	/* Proper page table entry exists, but no corresponding struct page */
	return -EEXIST;
}

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/*
 * FOLL_FORCE can write to even unwritable pte's, but only
 * after we've gone through a COW cycle and they are dirty.
 */
static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
{
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	return pte_write(pte) ||
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		((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
}

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static struct page *follow_page_pte(struct vm_area_struct *vma,
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		unsigned long address, pmd_t *pmd, unsigned int flags,
		struct dev_pagemap **pgmap)
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{
	struct mm_struct *mm = vma->vm_mm;
	struct page *page;
	spinlock_t *ptl;
	pte_t *ptep, pte;
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	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
			 (FOLL_PIN | FOLL_GET)))
		return ERR_PTR(-EINVAL);
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retry:
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	if (unlikely(pmd_bad(*pmd)))
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		return no_page_table(vma, flags);
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	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
	pte = *ptep;
	if (!pte_present(pte)) {
		swp_entry_t entry;
		/*
		 * KSM's break_ksm() relies upon recognizing a ksm page
		 * even while it is being migrated, so for that case we
		 * need migration_entry_wait().
		 */
		if (likely(!(flags & FOLL_MIGRATION)))
			goto no_page;
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		if (pte_none(pte))
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			goto no_page;
		entry = pte_to_swp_entry(pte);
		if (!is_migration_entry(entry))
			goto no_page;
		pte_unmap_unlock(ptep, ptl);
		migration_entry_wait(mm, pmd, address);
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		goto retry;
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	}
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	if ((flags & FOLL_NUMA) && pte_protnone(pte))
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		goto no_page;
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	if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
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		pte_unmap_unlock(ptep, ptl);
		return NULL;
	}
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	page = vm_normal_page(vma, address, pte);
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	if (!page && pte_devmap(pte) && (flags & FOLL_GET)) {
		/*
		 * Only return device mapping pages in the FOLL_GET case since
		 * they are only valid while holding the pgmap reference.
		 */
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		*pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap);
		if (*pgmap)
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			page = pte_page(pte);
		else
			goto no_page;
	} else if (unlikely(!page)) {
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		if (flags & FOLL_DUMP) {
			/* Avoid special (like zero) pages in core dumps */
			page = ERR_PTR(-EFAULT);
			goto out;
		}

		if (is_zero_pfn(pte_pfn(pte))) {
			page = pte_page(pte);
		} else {
			int ret;

			ret = follow_pfn_pte(vma, address, ptep, flags);
			page = ERR_PTR(ret);
			goto out;
		}
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	}

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	if (flags & FOLL_SPLIT && PageTransCompound(page)) {
		int ret;
		get_page(page);
		pte_unmap_unlock(ptep, ptl);
		lock_page(page);
		ret = split_huge_page(page);
		unlock_page(page);
		put_page(page);
		if (ret)
			return ERR_PTR(ret);
		goto retry;
	}

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	if (flags & FOLL_GET) {
		if (unlikely(!try_get_page(page))) {
			page = ERR_PTR(-ENOMEM);
			goto out;
		}
	}
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	if (flags & FOLL_TOUCH) {
		if ((flags & FOLL_WRITE) &&
		    !pte_dirty(pte) && !PageDirty(page))
			set_page_dirty(page);
		/*
		 * pte_mkyoung() would be more correct here, but atomic care
		 * is needed to avoid losing the dirty bit: it is easier to use
		 * mark_page_accessed().
		 */
		mark_page_accessed(page);
	}
E
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	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
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		/* Do not mlock pte-mapped THP */
		if (PageTransCompound(page))
			goto out;

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		/*
		 * The preliminary mapping check is mainly to avoid the
		 * pointless overhead of lock_page on the ZERO_PAGE
		 * which might bounce very badly if there is contention.
		 *
		 * If the page is already locked, we don't need to
		 * handle it now - vmscan will handle it later if and
		 * when it attempts to reclaim the page.
		 */
		if (page->mapping && trylock_page(page)) {
			lru_add_drain();  /* push cached pages to LRU */
			/*
			 * Because we lock page here, and migration is
			 * blocked by the pte's page reference, and we
			 * know the page is still mapped, we don't even
			 * need to check for file-cache page truncation.
			 */
			mlock_vma_page(page);
			unlock_page(page);
		}
	}
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out:
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	pte_unmap_unlock(ptep, ptl);
	return page;
no_page:
	pte_unmap_unlock(ptep, ptl);
	if (!pte_none(pte))
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		return NULL;
	return no_page_table(vma, flags);
}

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static struct page *follow_pmd_mask(struct vm_area_struct *vma,
				    unsigned long address, pud_t *pudp,
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				    unsigned int flags,
				    struct follow_page_context *ctx)
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{
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	pmd_t *pmd, pmdval;
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	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

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	pmd = pmd_offset(pudp, address);
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	/*
	 * The READ_ONCE() will stabilize the pmdval in a register or
	 * on the stack so that it will stop changing under the code.
	 */
	pmdval = READ_ONCE(*pmd);
	if (pmd_none(pmdval))
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		return no_page_table(vma, flags);
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	if (pmd_huge(pmdval) && is_vm_hugetlb_page(vma)) {
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		page = follow_huge_pmd(mm, address, pmd, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
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	}
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	if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
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		page = follow_huge_pd(vma, address,
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				      __hugepd(pmd_val(pmdval)), flags,
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				      PMD_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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retry:
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	if (!pmd_present(pmdval)) {
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		if (likely(!(flags & FOLL_MIGRATION)))
			return no_page_table(vma, flags);
		VM_BUG_ON(thp_migration_supported() &&
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				  !is_pmd_migration_entry(pmdval));
		if (is_pmd_migration_entry(pmdval))
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			pmd_migration_entry_wait(mm, pmd);
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		pmdval = READ_ONCE(*pmd);
		/*
		 * MADV_DONTNEED may convert the pmd to null because
		 * mmap_sem is held in read mode
		 */
		if (pmd_none(pmdval))
			return no_page_table(vma, flags);
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		goto retry;
	}
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	if (pmd_devmap(pmdval)) {
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		ptl = pmd_lock(mm, pmd);
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		page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
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		spin_unlock(ptl);
		if (page)
			return page;
	}
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	if (likely(!pmd_trans_huge(pmdval)))
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		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
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	if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
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		return no_page_table(vma, flags);

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retry_locked:
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	ptl = pmd_lock(mm, pmd);
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	if (unlikely(pmd_none(*pmd))) {
		spin_unlock(ptl);
		return no_page_table(vma, flags);
	}
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	if (unlikely(!pmd_present(*pmd))) {
		spin_unlock(ptl);
		if (likely(!(flags & FOLL_MIGRATION)))
			return no_page_table(vma, flags);
		pmd_migration_entry_wait(mm, pmd);
		goto retry_locked;
	}
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	if (unlikely(!pmd_trans_huge(*pmd))) {
		spin_unlock(ptl);
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		return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
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	}
S
Song Liu 已提交
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	if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) {
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		int ret;
		page = pmd_page(*pmd);
		if (is_huge_zero_page(page)) {
			spin_unlock(ptl);
			ret = 0;
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			split_huge_pmd(vma, pmd, address);
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			if (pmd_trans_unstable(pmd))
				ret = -EBUSY;
S
Song Liu 已提交
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		} else if (flags & FOLL_SPLIT) {
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			if (unlikely(!try_get_page(page))) {
				spin_unlock(ptl);
				return ERR_PTR(-ENOMEM);
			}
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			spin_unlock(ptl);
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			lock_page(page);
			ret = split_huge_page(page);
			unlock_page(page);
			put_page(page);
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			if (pmd_none(*pmd))
				return no_page_table(vma, flags);
S
Song Liu 已提交
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		} else {  /* flags & FOLL_SPLIT_PMD */
			spin_unlock(ptl);
			split_huge_pmd(vma, pmd, address);
			ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
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		}

		return ret ? ERR_PTR(ret) :
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			follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
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	}
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	page = follow_trans_huge_pmd(vma, address, pmd, flags);
	spin_unlock(ptl);
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	ctx->page_mask = HPAGE_PMD_NR - 1;
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	return page;
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}

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static struct page *follow_pud_mask(struct vm_area_struct *vma,
				    unsigned long address, p4d_t *p4dp,
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				    unsigned int flags,
				    struct follow_page_context *ctx)
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{
	pud_t *pud;
	spinlock_t *ptl;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

	pud = pud_offset(p4dp, address);
	if (pud_none(*pud))
		return no_page_table(vma, flags);
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	if (pud_huge(*pud) && is_vm_hugetlb_page(vma)) {
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		page = follow_huge_pud(mm, address, pud, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	if (is_hugepd(__hugepd(pud_val(*pud)))) {
		page = follow_huge_pd(vma, address,
				      __hugepd(pud_val(*pud)), flags,
				      PUD_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	if (pud_devmap(*pud)) {
		ptl = pud_lock(mm, pud);
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		page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
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		spin_unlock(ptl);
		if (page)
			return page;
	}
	if (unlikely(pud_bad(*pud)))
		return no_page_table(vma, flags);

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	return follow_pmd_mask(vma, address, pud, flags, ctx);
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}

static struct page *follow_p4d_mask(struct vm_area_struct *vma,
				    unsigned long address, pgd_t *pgdp,
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				    unsigned int flags,
				    struct follow_page_context *ctx)
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{
	p4d_t *p4d;
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	struct page *page;
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	p4d = p4d_offset(pgdp, address);
	if (p4d_none(*p4d))
		return no_page_table(vma, flags);
	BUILD_BUG_ON(p4d_huge(*p4d));
	if (unlikely(p4d_bad(*p4d)))
		return no_page_table(vma, flags);

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	if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
		page = follow_huge_pd(vma, address,
				      __hugepd(p4d_val(*p4d)), flags,
				      P4D_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	return follow_pud_mask(vma, address, p4d, flags, ctx);
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}

/**
 * follow_page_mask - look up a page descriptor from a user-virtual address
 * @vma: vm_area_struct mapping @address
 * @address: virtual address to look up
 * @flags: flags modifying lookup behaviour
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 * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
 *       pointer to output page_mask
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 *
 * @flags can have FOLL_ flags set, defined in <linux/mm.h>
 *
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 * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
 * the device's dev_pagemap metadata to avoid repeating expensive lookups.
 *
 * On output, the @ctx->page_mask is set according to the size of the page.
 *
 * Return: the mapped (struct page *), %NULL if no mapping exists, or
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 * an error pointer if there is a mapping to something not represented
 * by a page descriptor (see also vm_normal_page()).
 */
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static struct page *follow_page_mask(struct vm_area_struct *vma,
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			      unsigned long address, unsigned int flags,
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			      struct follow_page_context *ctx)
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{
	pgd_t *pgd;
	struct page *page;
	struct mm_struct *mm = vma->vm_mm;

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	ctx->page_mask = 0;
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	/* make this handle hugepd */
	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
	if (!IS_ERR(page)) {
		BUG_ON(flags & FOLL_GET);
		return page;
	}

	pgd = pgd_offset(mm, address);

	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
		return no_page_table(vma, flags);

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	if (pgd_huge(*pgd)) {
		page = follow_huge_pgd(mm, address, pgd, flags);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	if (is_hugepd(__hugepd(pgd_val(*pgd)))) {
		page = follow_huge_pd(vma, address,
				      __hugepd(pgd_val(*pgd)), flags,
				      PGDIR_SHIFT);
		if (page)
			return page;
		return no_page_table(vma, flags);
	}
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	return follow_p4d_mask(vma, address, pgd, flags, ctx);
}

struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
			 unsigned int foll_flags)
{
	struct follow_page_context ctx = { NULL };
	struct page *page;

	page = follow_page_mask(vma, address, foll_flags, &ctx);
	if (ctx.pgmap)
		put_dev_pagemap(ctx.pgmap);
	return page;
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}

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static int get_gate_page(struct mm_struct *mm, unsigned long address,
		unsigned int gup_flags, struct vm_area_struct **vma,
		struct page **page)
{
	pgd_t *pgd;
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	p4d_t *p4d;
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	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int ret = -EFAULT;

	/* user gate pages are read-only */
	if (gup_flags & FOLL_WRITE)
		return -EFAULT;
	if (address > TASK_SIZE)
		pgd = pgd_offset_k(address);
	else
		pgd = pgd_offset_gate(mm, address);
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	if (pgd_none(*pgd))
		return -EFAULT;
599
	p4d = p4d_offset(pgd, address);
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	if (p4d_none(*p4d))
		return -EFAULT;
602
	pud = pud_offset(p4d, address);
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	if (pud_none(*pud))
		return -EFAULT;
605
	pmd = pmd_offset(pud, address);
606
	if (!pmd_present(*pmd))
607 608 609 610 611 612 613 614 615 616 617 618 619 620
		return -EFAULT;
	VM_BUG_ON(pmd_trans_huge(*pmd));
	pte = pte_offset_map(pmd, address);
	if (pte_none(*pte))
		goto unmap;
	*vma = get_gate_vma(mm);
	if (!page)
		goto out;
	*page = vm_normal_page(*vma, address, *pte);
	if (!*page) {
		if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
			goto unmap;
		*page = pte_page(*pte);
	}
621 622 623 624
	if (unlikely(!try_get_page(*page))) {
		ret = -ENOMEM;
		goto unmap;
	}
625 626 627 628 629 630 631
out:
	ret = 0;
unmap:
	pte_unmap(pte);
	return ret;
}

632 633 634 635 636
/*
 * mmap_sem must be held on entry.  If @nonblocking != NULL and
 * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released.
 * If it is, *@nonblocking will be set to 0 and -EBUSY returned.
 */
637 638 639 640
static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
		unsigned long address, unsigned int *flags, int *nonblocking)
{
	unsigned int fault_flags = 0;
641
	vm_fault_t ret;
642

E
Eric B Munson 已提交
643 644 645
	/* mlock all present pages, but do not fault in new pages */
	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
		return -ENOENT;
646 647
	if (*flags & FOLL_WRITE)
		fault_flags |= FAULT_FLAG_WRITE;
648 649
	if (*flags & FOLL_REMOTE)
		fault_flags |= FAULT_FLAG_REMOTE;
650 651 652 653
	if (nonblocking)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
	if (*flags & FOLL_NOWAIT)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
654 655 656 657
	if (*flags & FOLL_TRIED) {
		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
		fault_flags |= FAULT_FLAG_TRIED;
	}
658

659
	ret = handle_mm_fault(vma, address, fault_flags);
660
	if (ret & VM_FAULT_ERROR) {
661 662 663 664
		int err = vm_fault_to_errno(ret, *flags);

		if (err)
			return err;
665 666 667 668 669 670 671 672 673 674 675
		BUG();
	}

	if (tsk) {
		if (ret & VM_FAULT_MAJOR)
			tsk->maj_flt++;
		else
			tsk->min_flt++;
	}

	if (ret & VM_FAULT_RETRY) {
676
		if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
677 678 679 680 681 682 683 684 685 686 687 688 689 690
			*nonblocking = 0;
		return -EBUSY;
	}

	/*
	 * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when
	 * necessary, even if maybe_mkwrite decided not to set pte_write. We
	 * can thus safely do subsequent page lookups as if they were reads.
	 * But only do so when looping for pte_write is futile: in some cases
	 * userspace may also be wanting to write to the gotten user page,
	 * which a read fault here might prevent (a readonly page might get
	 * reCOWed by userspace write).
	 */
	if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
691
		*flags |= FOLL_COW;
692 693 694
	return 0;
}

695 696 697
static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
{
	vm_flags_t vm_flags = vma->vm_flags;
698 699
	int write = (gup_flags & FOLL_WRITE);
	int foreign = (gup_flags & FOLL_REMOTE);
700 701 702 703

	if (vm_flags & (VM_IO | VM_PFNMAP))
		return -EFAULT;

704 705 706
	if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
		return -EFAULT;

707
	if (write) {
708 709 710 711 712 713 714 715 716 717 718 719
		if (!(vm_flags & VM_WRITE)) {
			if (!(gup_flags & FOLL_FORCE))
				return -EFAULT;
			/*
			 * We used to let the write,force case do COW in a
			 * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
			 * set a breakpoint in a read-only mapping of an
			 * executable, without corrupting the file (yet only
			 * when that file had been opened for writing!).
			 * Anon pages in shared mappings are surprising: now
			 * just reject it.
			 */
720
			if (!is_cow_mapping(vm_flags))
721 722 723 724 725 726 727 728 729 730 731 732
				return -EFAULT;
		}
	} else if (!(vm_flags & VM_READ)) {
		if (!(gup_flags & FOLL_FORCE))
			return -EFAULT;
		/*
		 * Is there actually any vma we can reach here which does not
		 * have VM_MAYREAD set?
		 */
		if (!(vm_flags & VM_MAYREAD))
			return -EFAULT;
	}
733 734 735 736 737
	/*
	 * gups are always data accesses, not instruction
	 * fetches, so execute=false here
	 */
	if (!arch_vma_access_permitted(vma, write, false, foreign))
738
		return -EFAULT;
739 740 741
	return 0;
}

742 743 744 745 746 747 748 749 750 751 752 753 754 755
/**
 * __get_user_pages() - pin user pages in memory
 * @tsk:	task_struct of target task
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @gup_flags:	flags modifying pin behaviour
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
 * @nonblocking: whether waiting for disk IO or mmap_sem contention
 *
756 757 758 759 760 761 762 763 764 765 766
 * Returns either number of pages pinned (which may be less than the
 * number requested), or an error. Details about the return value:
 *
 * -- If nr_pages is 0, returns 0.
 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
 * -- If nr_pages is >0, and some pages were pinned, returns the number of
 *    pages pinned. Again, this may be less than nr_pages.
 *
 * The caller is responsible for releasing returned @pages, via put_page().
 *
 * @vmas are valid only as long as mmap_sem is held.
767
 *
768
 * Must be called with mmap_sem held.  It may be released.  See below.
769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790
 *
 * __get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * __get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
 * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
 * the page is written to, set_page_dirty (or set_page_dirty_lock, as
 * appropriate) must be called after the page is finished with, and
 * before put_page is called.
 *
 * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
 * or mmap_sem contention, and if waiting is needed to pin all pages,
791 792 793 794 795 796 797 798
 * *@nonblocking will be set to 0.  Further, if @gup_flags does not
 * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in
 * this case.
 *
 * A caller using such a combination of @nonblocking and @gup_flags
 * must therefore hold the mmap_sem for reading only, and recognize
 * when it's been released.  Otherwise, it must be held for either
 * reading or writing and will not be released.
799 800 801 802 803
 *
 * In most cases, get_user_pages or get_user_pages_fast should be used
 * instead of __get_user_pages. __get_user_pages should be used only if
 * you need some special @gup_flags.
 */
L
Lorenzo Stoakes 已提交
804
static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
805 806 807 808
		unsigned long start, unsigned long nr_pages,
		unsigned int gup_flags, struct page **pages,
		struct vm_area_struct **vmas, int *nonblocking)
{
809
	long ret = 0, i = 0;
810
	struct vm_area_struct *vma = NULL;
811
	struct follow_page_context ctx = { NULL };
812 813 814 815

	if (!nr_pages)
		return 0;

816 817
	start = untagged_addr(start);

818
	VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
819 820 821 822 823 824 825 826 827 828

	/*
	 * If FOLL_FORCE is set then do not force a full fault as the hinting
	 * fault information is unrelated to the reference behaviour of a task
	 * using the address space
	 */
	if (!(gup_flags & FOLL_FORCE))
		gup_flags |= FOLL_NUMA;

	do {
829 830 831 832 833 834 835 836 837 838 839 840
		struct page *page;
		unsigned int foll_flags = gup_flags;
		unsigned int page_increm;

		/* first iteration or cross vma bound */
		if (!vma || start >= vma->vm_end) {
			vma = find_extend_vma(mm, start);
			if (!vma && in_gate_area(mm, start)) {
				ret = get_gate_page(mm, start & PAGE_MASK,
						gup_flags, &vma,
						pages ? &pages[i] : NULL);
				if (ret)
841
					goto out;
842
				ctx.page_mask = 0;
843 844
				goto next_page;
			}
845

846 847 848 849
			if (!vma || check_vma_flags(vma, gup_flags)) {
				ret = -EFAULT;
				goto out;
			}
850 851 852
			if (is_vm_hugetlb_page(vma)) {
				i = follow_hugetlb_page(mm, vma, pages, vmas,
						&start, &nr_pages, i,
853
						gup_flags, nonblocking);
854
				continue;
855
			}
856 857 858 859 860 861
		}
retry:
		/*
		 * If we have a pending SIGKILL, don't keep faulting pages and
		 * potentially allocating memory.
		 */
862
		if (fatal_signal_pending(current)) {
863 864 865
			ret = -ERESTARTSYS;
			goto out;
		}
866
		cond_resched();
867 868

		page = follow_page_mask(vma, start, foll_flags, &ctx);
869 870 871 872 873 874
		if (!page) {
			ret = faultin_page(tsk, vma, start, &foll_flags,
					nonblocking);
			switch (ret) {
			case 0:
				goto retry;
875 876 877
			case -EBUSY:
				ret = 0;
				/* FALLTHRU */
878 879 880
			case -EFAULT:
			case -ENOMEM:
			case -EHWPOISON:
881
				goto out;
882 883
			case -ENOENT:
				goto next_page;
884
			}
885
			BUG();
886 887 888 889 890 891 892
		} else if (PTR_ERR(page) == -EEXIST) {
			/*
			 * Proper page table entry exists, but no corresponding
			 * struct page.
			 */
			goto next_page;
		} else if (IS_ERR(page)) {
893 894
			ret = PTR_ERR(page);
			goto out;
895
		}
896 897 898 899
		if (pages) {
			pages[i] = page;
			flush_anon_page(vma, page, start);
			flush_dcache_page(page);
900
			ctx.page_mask = 0;
901 902
		}
next_page:
903 904
		if (vmas) {
			vmas[i] = vma;
905
			ctx.page_mask = 0;
906
		}
907
		page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask);
908 909 910 911 912
		if (page_increm > nr_pages)
			page_increm = nr_pages;
		i += page_increm;
		start += page_increm * PAGE_SIZE;
		nr_pages -= page_increm;
913
	} while (nr_pages);
914 915 916 917
out:
	if (ctx.pgmap)
		put_dev_pagemap(ctx.pgmap);
	return i ? i : ret;
918 919
}

920 921
static bool vma_permits_fault(struct vm_area_struct *vma,
			      unsigned int fault_flags)
922
{
923 924
	bool write   = !!(fault_flags & FAULT_FLAG_WRITE);
	bool foreign = !!(fault_flags & FAULT_FLAG_REMOTE);
925
	vm_flags_t vm_flags = write ? VM_WRITE : VM_READ;
926 927 928 929

	if (!(vm_flags & vma->vm_flags))
		return false;

930 931
	/*
	 * The architecture might have a hardware protection
932
	 * mechanism other than read/write that can deny access.
933 934 935
	 *
	 * gup always represents data access, not instruction
	 * fetches, so execute=false here:
936
	 */
937
	if (!arch_vma_access_permitted(vma, write, false, foreign))
938 939
		return false;

940 941 942
	return true;
}

943 944 945 946 947 948 949
/*
 * fixup_user_fault() - manually resolve a user page fault
 * @tsk:	the task_struct to use for page fault accounting, or
 *		NULL if faults are not to be recorded.
 * @mm:		mm_struct of target mm
 * @address:	user address
 * @fault_flags:flags to pass down to handle_mm_fault()
950 951
 * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
 *		does not allow retry
952 953 954 955 956 957 958 959 960 961 962
 *
 * This is meant to be called in the specific scenario where for locking reasons
 * we try to access user memory in atomic context (within a pagefault_disable()
 * section), this returns -EFAULT, and we want to resolve the user fault before
 * trying again.
 *
 * Typically this is meant to be used by the futex code.
 *
 * The main difference with get_user_pages() is that this function will
 * unconditionally call handle_mm_fault() which will in turn perform all the
 * necessary SW fixup of the dirty and young bits in the PTE, while
963
 * get_user_pages() only guarantees to update these in the struct page.
964 965 966 967 968 969
 *
 * This is important for some architectures where those bits also gate the
 * access permission to the page because they are maintained in software.  On
 * such architectures, gup() will not be enough to make a subsequent access
 * succeed.
 *
970 971
 * This function will not return with an unlocked mmap_sem. So it has not the
 * same semantics wrt the @mm->mmap_sem as does filemap_fault().
972 973
 */
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
974 975
		     unsigned long address, unsigned int fault_flags,
		     bool *unlocked)
976 977
{
	struct vm_area_struct *vma;
978
	vm_fault_t ret, major = 0;
979

980 981
	address = untagged_addr(address);

982 983
	if (unlocked)
		fault_flags |= FAULT_FLAG_ALLOW_RETRY;
984

985
retry:
986 987 988 989
	vma = find_extend_vma(mm, address);
	if (!vma || address < vma->vm_start)
		return -EFAULT;

990
	if (!vma_permits_fault(vma, fault_flags))
991 992
		return -EFAULT;

993
	ret = handle_mm_fault(vma, address, fault_flags);
994
	major |= ret & VM_FAULT_MAJOR;
995
	if (ret & VM_FAULT_ERROR) {
996 997 998 999
		int err = vm_fault_to_errno(ret, 0);

		if (err)
			return err;
1000 1001
		BUG();
	}
1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012

	if (ret & VM_FAULT_RETRY) {
		down_read(&mm->mmap_sem);
		if (!(fault_flags & FAULT_FLAG_TRIED)) {
			*unlocked = true;
			fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
			fault_flags |= FAULT_FLAG_TRIED;
			goto retry;
		}
	}

1013
	if (tsk) {
1014
		if (major)
1015 1016 1017 1018 1019 1020
			tsk->maj_flt++;
		else
			tsk->min_flt++;
	}
	return 0;
}
1021
EXPORT_SYMBOL_GPL(fixup_user_fault);
1022

1023 1024 1025 1026 1027 1028
static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
						struct mm_struct *mm,
						unsigned long start,
						unsigned long nr_pages,
						struct page **pages,
						struct vm_area_struct **vmas,
1029
						int *locked,
1030
						unsigned int flags)
1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041
{
	long ret, pages_done;
	bool lock_dropped;

	if (locked) {
		/* if VM_FAULT_RETRY can be returned, vmas become invalid */
		BUG_ON(vmas);
		/* check caller initialized locked */
		BUG_ON(*locked != 1);
	}

1042 1043 1044 1045 1046 1047 1048 1049 1050 1051
	/*
	 * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior
	 * is to set FOLL_GET if the caller wants pages[] filled in (but has
	 * carelessly failed to specify FOLL_GET), so keep doing that, but only
	 * for FOLL_GET, not for the newer FOLL_PIN.
	 *
	 * FOLL_PIN always expects pages to be non-null, but no need to assert
	 * that here, as any failures will be obvious enough.
	 */
	if (pages && !(flags & FOLL_PIN))
1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075
		flags |= FOLL_GET;

	pages_done = 0;
	lock_dropped = false;
	for (;;) {
		ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages,
				       vmas, locked);
		if (!locked)
			/* VM_FAULT_RETRY couldn't trigger, bypass */
			return ret;

		/* VM_FAULT_RETRY cannot return errors */
		if (!*locked) {
			BUG_ON(ret < 0);
			BUG_ON(ret >= nr_pages);
		}

		if (ret > 0) {
			nr_pages -= ret;
			pages_done += ret;
			if (!nr_pages)
				break;
		}
		if (*locked) {
1076 1077 1078 1079
			/*
			 * VM_FAULT_RETRY didn't trigger or it was a
			 * FOLL_NOWAIT.
			 */
1080 1081 1082 1083
			if (!pages_done)
				pages_done = ret;
			break;
		}
1084 1085 1086 1087 1088 1089
		/*
		 * VM_FAULT_RETRY triggered, so seek to the faulting offset.
		 * For the prefault case (!pages) we only update counts.
		 */
		if (likely(pages))
			pages += ret;
1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111
		start += ret << PAGE_SHIFT;

		/*
		 * Repeat on the address that fired VM_FAULT_RETRY
		 * without FAULT_FLAG_ALLOW_RETRY but with
		 * FAULT_FLAG_TRIED.
		 */
		*locked = 1;
		lock_dropped = true;
		down_read(&mm->mmap_sem);
		ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED,
				       pages, NULL, NULL);
		if (ret != 1) {
			BUG_ON(ret > 1);
			if (!pages_done)
				pages_done = ret;
			break;
		}
		nr_pages--;
		pages_done++;
		if (!nr_pages)
			break;
1112 1113
		if (likely(pages))
			pages++;
1114 1115
		start += PAGE_SIZE;
	}
1116
	if (lock_dropped && *locked) {
1117 1118 1119 1120 1121 1122 1123 1124 1125 1126
		/*
		 * We must let the caller know we temporarily dropped the lock
		 * and so the critical section protected by it was lost.
		 */
		up_read(&mm->mmap_sem);
		*locked = 0;
	}
	return pages_done;
}

1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272
/**
 * populate_vma_page_range() -  populate a range of pages in the vma.
 * @vma:   target vma
 * @start: start address
 * @end:   end address
 * @nonblocking:
 *
 * This takes care of mlocking the pages too if VM_LOCKED is set.
 *
 * return 0 on success, negative error code on error.
 *
 * vma->vm_mm->mmap_sem must be held.
 *
 * If @nonblocking is NULL, it may be held for read or write and will
 * be unperturbed.
 *
 * If @nonblocking is non-NULL, it must held for read only and may be
 * released.  If it's released, *@nonblocking will be set to 0.
 */
long populate_vma_page_range(struct vm_area_struct *vma,
		unsigned long start, unsigned long end, int *nonblocking)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long nr_pages = (end - start) / PAGE_SIZE;
	int gup_flags;

	VM_BUG_ON(start & ~PAGE_MASK);
	VM_BUG_ON(end   & ~PAGE_MASK);
	VM_BUG_ON_VMA(start < vma->vm_start, vma);
	VM_BUG_ON_VMA(end   > vma->vm_end, vma);
	VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);

	gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK;
	if (vma->vm_flags & VM_LOCKONFAULT)
		gup_flags &= ~FOLL_POPULATE;
	/*
	 * We want to touch writable mappings with a write fault in order
	 * to break COW, except for shared mappings because these don't COW
	 * and we would not want to dirty them for nothing.
	 */
	if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
		gup_flags |= FOLL_WRITE;

	/*
	 * We want mlock to succeed for regions that have any permissions
	 * other than PROT_NONE.
	 */
	if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
		gup_flags |= FOLL_FORCE;

	/*
	 * We made sure addr is within a VMA, so the following will
	 * not result in a stack expansion that recurses back here.
	 */
	return __get_user_pages(current, mm, start, nr_pages, gup_flags,
				NULL, NULL, nonblocking);
}

/*
 * __mm_populate - populate and/or mlock pages within a range of address space.
 *
 * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
 * flags. VMAs must be already marked with the desired vm_flags, and
 * mmap_sem must not be held.
 */
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
{
	struct mm_struct *mm = current->mm;
	unsigned long end, nstart, nend;
	struct vm_area_struct *vma = NULL;
	int locked = 0;
	long ret = 0;

	end = start + len;

	for (nstart = start; nstart < end; nstart = nend) {
		/*
		 * We want to fault in pages for [nstart; end) address range.
		 * Find first corresponding VMA.
		 */
		if (!locked) {
			locked = 1;
			down_read(&mm->mmap_sem);
			vma = find_vma(mm, nstart);
		} else if (nstart >= vma->vm_end)
			vma = vma->vm_next;
		if (!vma || vma->vm_start >= end)
			break;
		/*
		 * Set [nstart; nend) to intersection of desired address
		 * range with the first VMA. Also, skip undesirable VMA types.
		 */
		nend = min(end, vma->vm_end);
		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
			continue;
		if (nstart < vma->vm_start)
			nstart = vma->vm_start;
		/*
		 * Now fault in a range of pages. populate_vma_page_range()
		 * double checks the vma flags, so that it won't mlock pages
		 * if the vma was already munlocked.
		 */
		ret = populate_vma_page_range(vma, nstart, nend, &locked);
		if (ret < 0) {
			if (ignore_errors) {
				ret = 0;
				continue;	/* continue at next VMA */
			}
			break;
		}
		nend = nstart + ret * PAGE_SIZE;
		ret = 0;
	}
	if (locked)
		up_read(&mm->mmap_sem);
	return ret;	/* 0 or negative error code */
}

/**
 * get_dump_page() - pin user page in memory while writing it to core dump
 * @addr: user address
 *
 * Returns struct page pointer of user page pinned for dump,
 * to be freed afterwards by put_page().
 *
 * Returns NULL on any kind of failure - a hole must then be inserted into
 * the corefile, to preserve alignment with its headers; and also returns
 * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
 * allowing a hole to be left in the corefile to save diskspace.
 *
 * Called without mmap_sem, but after all other threads have been killed.
 */
#ifdef CONFIG_ELF_CORE
struct page *get_dump_page(unsigned long addr)
{
	struct vm_area_struct *vma;
	struct page *page;

	if (__get_user_pages(current, current->mm, addr, 1,
			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
			     NULL) < 1)
		return NULL;
	flush_cache_page(vma, addr, page_to_pfn(page));
	return page;
}
#endif /* CONFIG_ELF_CORE */
1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317
#else /* CONFIG_MMU */
static long __get_user_pages_locked(struct task_struct *tsk,
		struct mm_struct *mm, unsigned long start,
		unsigned long nr_pages, struct page **pages,
		struct vm_area_struct **vmas, int *locked,
		unsigned int foll_flags)
{
	struct vm_area_struct *vma;
	unsigned long vm_flags;
	int i;

	/* calculate required read or write permissions.
	 * If FOLL_FORCE is set, we only require the "MAY" flags.
	 */
	vm_flags  = (foll_flags & FOLL_WRITE) ?
			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
	vm_flags &= (foll_flags & FOLL_FORCE) ?
			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);

	for (i = 0; i < nr_pages; i++) {
		vma = find_vma(mm, start);
		if (!vma)
			goto finish_or_fault;

		/* protect what we can, including chardevs */
		if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
		    !(vm_flags & vma->vm_flags))
			goto finish_or_fault;

		if (pages) {
			pages[i] = virt_to_page(start);
			if (pages[i])
				get_page(pages[i]);
		}
		if (vmas)
			vmas[i] = vma;
		start = (start + PAGE_SIZE) & PAGE_MASK;
	}

	return i;

finish_or_fault:
	return i ? : -EFAULT;
}
#endif /* !CONFIG_MMU */
1318

1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390
#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
{
	long i;
	struct vm_area_struct *vma_prev = NULL;

	for (i = 0; i < nr_pages; i++) {
		struct vm_area_struct *vma = vmas[i];

		if (vma == vma_prev)
			continue;

		vma_prev = vma;

		if (vma_is_fsdax(vma))
			return true;
	}
	return false;
}

#ifdef CONFIG_CMA
static struct page *new_non_cma_page(struct page *page, unsigned long private)
{
	/*
	 * We want to make sure we allocate the new page from the same node
	 * as the source page.
	 */
	int nid = page_to_nid(page);
	/*
	 * Trying to allocate a page for migration. Ignore allocation
	 * failure warnings. We don't force __GFP_THISNODE here because
	 * this node here is the node where we have CMA reservation and
	 * in some case these nodes will have really less non movable
	 * allocation memory.
	 */
	gfp_t gfp_mask = GFP_USER | __GFP_NOWARN;

	if (PageHighMem(page))
		gfp_mask |= __GFP_HIGHMEM;

#ifdef CONFIG_HUGETLB_PAGE
	if (PageHuge(page)) {
		struct hstate *h = page_hstate(page);
		/*
		 * We don't want to dequeue from the pool because pool pages will
		 * mostly be from the CMA region.
		 */
		return alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
	}
#endif
	if (PageTransHuge(page)) {
		struct page *thp;
		/*
		 * ignore allocation failure warnings
		 */
		gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_NOWARN;

		/*
		 * Remove the movable mask so that we don't allocate from
		 * CMA area again.
		 */
		thp_gfpmask &= ~__GFP_MOVABLE;
		thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER);
		if (!thp)
			return NULL;
		prep_transhuge_page(thp);
		return thp;
	}

	return __alloc_pages_node(nid, gfp_mask, 0);
}

1391 1392 1393 1394
static long check_and_migrate_cma_pages(struct task_struct *tsk,
					struct mm_struct *mm,
					unsigned long start,
					unsigned long nr_pages,
1395
					struct page **pages,
1396 1397
					struct vm_area_struct **vmas,
					unsigned int gup_flags)
1398
{
1399 1400
	unsigned long i;
	unsigned long step;
1401 1402 1403
	bool drain_allow = true;
	bool migrate_allow = true;
	LIST_HEAD(cma_page_list);
1404
	long ret = nr_pages;
1405 1406

check_again:
1407 1408 1409 1410 1411 1412 1413 1414
	for (i = 0; i < nr_pages;) {

		struct page *head = compound_head(pages[i]);

		/*
		 * gup may start from a tail page. Advance step by the left
		 * part.
		 */
1415
		step = compound_nr(head) - (pages[i] - head);
1416 1417 1418 1419 1420
		/*
		 * If we get a page from the CMA zone, since we are going to
		 * be pinning these entries, we might as well move them out
		 * of the CMA zone if possible.
		 */
1421 1422
		if (is_migrate_cma_page(head)) {
			if (PageHuge(head))
1423
				isolate_huge_page(head, &cma_page_list);
1424
			else {
1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438
				if (!PageLRU(head) && drain_allow) {
					lru_add_drain_all();
					drain_allow = false;
				}

				if (!isolate_lru_page(head)) {
					list_add_tail(&head->lru, &cma_page_list);
					mod_node_page_state(page_pgdat(head),
							    NR_ISOLATED_ANON +
							    page_is_file_cache(head),
							    hpage_nr_pages(head));
				}
			}
		}
1439 1440

		i += step;
1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461
	}

	if (!list_empty(&cma_page_list)) {
		/*
		 * drop the above get_user_pages reference.
		 */
		for (i = 0; i < nr_pages; i++)
			put_page(pages[i]);

		if (migrate_pages(&cma_page_list, new_non_cma_page,
				  NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
			/*
			 * some of the pages failed migration. Do get_user_pages
			 * without migration.
			 */
			migrate_allow = false;

			if (!list_empty(&cma_page_list))
				putback_movable_pages(&cma_page_list);
		}
		/*
1462 1463 1464
		 * We did migrate all the pages, Try to get the page references
		 * again migrating any new CMA pages which we failed to isolate
		 * earlier.
1465
		 */
1466
		ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
1467 1468 1469
						   pages, vmas, NULL,
						   gup_flags);

1470 1471
		if ((ret > 0) && migrate_allow) {
			nr_pages = ret;
1472 1473 1474 1475 1476
			drain_allow = true;
			goto check_again;
		}
	}

1477
	return ret;
1478 1479
}
#else
1480 1481 1482 1483 1484 1485 1486
static long check_and_migrate_cma_pages(struct task_struct *tsk,
					struct mm_struct *mm,
					unsigned long start,
					unsigned long nr_pages,
					struct page **pages,
					struct vm_area_struct **vmas,
					unsigned int gup_flags)
1487 1488 1489
{
	return nr_pages;
}
1490
#endif /* CONFIG_CMA */
1491

1492
/*
1493 1494
 * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
 * allows us to process the FOLL_LONGTERM flag.
1495
 */
1496 1497 1498 1499 1500 1501 1502
static long __gup_longterm_locked(struct task_struct *tsk,
				  struct mm_struct *mm,
				  unsigned long start,
				  unsigned long nr_pages,
				  struct page **pages,
				  struct vm_area_struct **vmas,
				  unsigned int gup_flags)
1503
{
1504 1505
	struct vm_area_struct **vmas_tmp = vmas;
	unsigned long flags = 0;
1506 1507
	long rc, i;

1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519
	if (gup_flags & FOLL_LONGTERM) {
		if (!pages)
			return -EINVAL;

		if (!vmas_tmp) {
			vmas_tmp = kcalloc(nr_pages,
					   sizeof(struct vm_area_struct *),
					   GFP_KERNEL);
			if (!vmas_tmp)
				return -ENOMEM;
		}
		flags = memalloc_nocma_save();
1520 1521
	}

1522 1523
	rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
				     vmas_tmp, NULL, gup_flags);
1524

1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538
	if (gup_flags & FOLL_LONGTERM) {
		memalloc_nocma_restore(flags);
		if (rc < 0)
			goto out;

		if (check_dax_vmas(vmas_tmp, rc)) {
			for (i = 0; i < rc; i++)
				put_page(pages[i]);
			rc = -EOPNOTSUPP;
			goto out;
		}

		rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
						 vmas_tmp, gup_flags);
1539
	}
1540 1541

out:
1542 1543
	if (vmas_tmp != vmas)
		kfree(vmas_tmp);
1544 1545
	return rc;
}
1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559
#else /* !CONFIG_FS_DAX && !CONFIG_CMA */
static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
						  struct mm_struct *mm,
						  unsigned long start,
						  unsigned long nr_pages,
						  struct page **pages,
						  struct vm_area_struct **vmas,
						  unsigned int flags)
{
	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
				       NULL, flags);
}
#endif /* CONFIG_FS_DAX || CONFIG_CMA */

1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621
/*
 * get_user_pages_remote() - pin user pages in memory
 * @tsk:	the task_struct to use for page fault accounting, or
 *		NULL if faults are not to be recorded.
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @gup_flags:	flags modifying lookup behaviour
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
 * @locked:	pointer to lock flag indicating whether lock is held and
 *		subsequently whether VM_FAULT_RETRY functionality can be
 *		utilised. Lock must initially be held.
 *
 * Returns either number of pages pinned (which may be less than the
 * number requested), or an error. Details about the return value:
 *
 * -- If nr_pages is 0, returns 0.
 * -- If nr_pages is >0, but no pages were pinned, returns -errno.
 * -- If nr_pages is >0, and some pages were pinned, returns the number of
 *    pages pinned. Again, this may be less than nr_pages.
 *
 * The caller is responsible for releasing returned @pages, via put_page().
 *
 * @vmas are valid only as long as mmap_sem is held.
 *
 * Must be called with mmap_sem held for read or write.
 *
 * get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
 * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
 * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
 * be called after the page is finished with, and before put_page is called.
 *
 * get_user_pages is typically used for fewer-copy IO operations, to get a
 * handle on the memory by some means other than accesses via the user virtual
 * addresses. The pages may be submitted for DMA to devices or accessed via
 * their kernel linear mapping (via the kmap APIs). Care should be taken to
 * use the correct cache flushing APIs.
 *
 * See also get_user_pages_fast, for performance critical applications.
 *
 * get_user_pages should be phased out in favor of
 * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing
 * should use get_user_pages because it cannot pass
 * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault.
 */
1622
#ifdef CONFIG_MMU
1623 1624 1625 1626 1627
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
		unsigned long start, unsigned long nr_pages,
		unsigned int gup_flags, struct page **pages,
		struct vm_area_struct **vmas, int *locked)
{
1628 1629 1630 1631 1632 1633 1634
	/*
	 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
	 * never directly by the caller, so enforce that with an assertion:
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
		return -EINVAL;

1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659
	/*
	 * Parts of FOLL_LONGTERM behavior are incompatible with
	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
	 * vmas. However, this only comes up if locked is set, and there are
	 * callers that do request FOLL_LONGTERM, but do not set locked. So,
	 * allow what we can.
	 */
	if (gup_flags & FOLL_LONGTERM) {
		if (WARN_ON_ONCE(locked))
			return -EINVAL;
		/*
		 * This will check the vmas (even if our vmas arg is NULL)
		 * and return -ENOTSUPP if DAX isn't allowed in this case:
		 */
		return __gup_longterm_locked(tsk, mm, start, nr_pages, pages,
					     vmas, gup_flags | FOLL_TOUCH |
					     FOLL_REMOTE);
	}

	return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
				       locked,
				       gup_flags | FOLL_TOUCH | FOLL_REMOTE);
}
EXPORT_SYMBOL(get_user_pages_remote);

1660 1661 1662 1663 1664 1665 1666 1667 1668 1669
#else /* CONFIG_MMU */
long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
			   unsigned long start, unsigned long nr_pages,
			   unsigned int gup_flags, struct page **pages,
			   struct vm_area_struct **vmas, int *locked)
{
	return 0;
}
#endif /* !CONFIG_MMU */

1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680
/*
 * This is the same as get_user_pages_remote(), just with a
 * less-flexible calling convention where we assume that the task
 * and mm being operated on are the current task's and don't allow
 * passing of a locked parameter.  We also obviously don't pass
 * FOLL_REMOTE in here.
 */
long get_user_pages(unsigned long start, unsigned long nr_pages,
		unsigned int gup_flags, struct page **pages,
		struct vm_area_struct **vmas)
{
1681 1682 1683 1684 1685 1686 1687
	/*
	 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
	 * never directly by the caller, so enforce that with an assertion:
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
		return -EINVAL;

1688 1689 1690 1691
	return __gup_longterm_locked(current, current->mm, start, nr_pages,
				     pages, vmas, gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(get_user_pages);
1692

1693 1694 1695 1696
/*
 * We can leverage the VM_FAULT_RETRY functionality in the page fault
 * paths better by using either get_user_pages_locked() or
 * get_user_pages_unlocked().
1697
 *
1698
 * get_user_pages_locked() is suitable to replace the form:
1699
 *
1700 1701 1702 1703
 *      down_read(&mm->mmap_sem);
 *      do_something()
 *      get_user_pages(tsk, mm, ..., pages, NULL);
 *      up_read(&mm->mmap_sem);
1704
 *
1705
 *  to:
1706
 *
1707 1708 1709 1710 1711 1712
 *      int locked = 1;
 *      down_read(&mm->mmap_sem);
 *      do_something()
 *      get_user_pages_locked(tsk, mm, ..., pages, &locked);
 *      if (locked)
 *          up_read(&mm->mmap_sem);
1713
 */
1714 1715 1716
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
			   unsigned int gup_flags, struct page **pages,
			   int *locked)
1717 1718
{
	/*
1719 1720 1721 1722
	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
	 * vmas.  As there are no users of this flag in this call we simply
	 * disallow this option for now.
1723
	 */
1724 1725
	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
		return -EINVAL;
1726

1727 1728 1729
	return __get_user_pages_locked(current, current->mm, start, nr_pages,
				       pages, NULL, locked,
				       gup_flags | FOLL_TOUCH);
1730
}
1731
EXPORT_SYMBOL(get_user_pages_locked);
1732 1733

/*
1734
 * get_user_pages_unlocked() is suitable to replace the form:
1735
 *
1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746
 *      down_read(&mm->mmap_sem);
 *      get_user_pages(tsk, mm, ..., pages, NULL);
 *      up_read(&mm->mmap_sem);
 *
 *  with:
 *
 *      get_user_pages_unlocked(tsk, mm, ..., pages);
 *
 * It is functionally equivalent to get_user_pages_fast so
 * get_user_pages_fast should be used instead if specific gup_flags
 * (e.g. FOLL_FORCE) are not required.
1747
 */
1748 1749
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
			     struct page **pages, unsigned int gup_flags)
1750 1751
{
	struct mm_struct *mm = current->mm;
1752 1753
	int locked = 1;
	long ret;
1754

1755 1756 1757 1758 1759 1760 1761 1762
	/*
	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
	 * vmas.  As there are no users of this flag in this call we simply
	 * disallow this option for now.
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
		return -EINVAL;
1763

1764 1765 1766
	down_read(&mm->mmap_sem);
	ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL,
				      &locked, gup_flags | FOLL_TOUCH);
1767 1768
	if (locked)
		up_read(&mm->mmap_sem);
1769
	return ret;
1770
}
1771
EXPORT_SYMBOL(get_user_pages_unlocked);
1772 1773

/*
1774
 * Fast GUP
1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794
 *
 * get_user_pages_fast attempts to pin user pages by walking the page
 * tables directly and avoids taking locks. Thus the walker needs to be
 * protected from page table pages being freed from under it, and should
 * block any THP splits.
 *
 * One way to achieve this is to have the walker disable interrupts, and
 * rely on IPIs from the TLB flushing code blocking before the page table
 * pages are freed. This is unsuitable for architectures that do not need
 * to broadcast an IPI when invalidating TLBs.
 *
 * Another way to achieve this is to batch up page table containing pages
 * belonging to more than one mm_user, then rcu_sched a callback to free those
 * pages. Disabling interrupts will allow the fast_gup walker to both block
 * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
 * (which is a relatively rare event). The code below adopts this strategy.
 *
 * Before activating this code, please be aware that the following assumptions
 * are currently made:
 *
1795
 *  *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
1796
 *  free pages containing page tables or TLB flushing requires IPI broadcast.
1797 1798 1799 1800 1801 1802 1803 1804 1805
 *
 *  *) ptes can be read atomically by the architecture.
 *
 *  *) access_ok is sufficient to validate userspace address ranges.
 *
 * The last two assumptions can be relaxed by the addition of helper functions.
 *
 * This code is based heavily on the PowerPC implementation by Nick Piggin.
 */
1806
#ifdef CONFIG_HAVE_FAST_GUP
1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841
#ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
/*
 * WARNING: only to be used in the get_user_pages_fast() implementation.
 *
 * 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 sometimes
 * that is not possible (e.g. without expensive cmpxchg8b on x86_32 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 gotten 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'. Because get_user_pages_fast() only
 * operates on present ptes we're safe.
 */
static inline pte_t gup_get_pte(pte_t *ptep)
{
	pte_t pte;
1842

1843 1844 1845 1846 1847 1848 1849 1850 1851 1852
	do {
		pte.pte_low = ptep->pte_low;
		smp_rmb();
		pte.pte_high = ptep->pte_high;
		smp_rmb();
	} while (unlikely(pte.pte_low != ptep->pte_low));

	return pte;
}
#else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
1853
/*
1854
 * We require that the PTE can be read atomically.
1855 1856 1857 1858 1859
 */
static inline pte_t gup_get_pte(pte_t *ptep)
{
	return READ_ONCE(*ptep);
}
1860
#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
1861

1862 1863
static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
					    struct page **pages)
1864 1865 1866 1867 1868 1869 1870 1871 1872
{
	while ((*nr) - nr_start) {
		struct page *page = pages[--(*nr)];

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

1873
#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
1874
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1875
			 unsigned int flags, struct page **pages, int *nr)
1876
{
1877 1878
	struct dev_pagemap *pgmap = NULL;
	int nr_start = *nr, ret = 0;
1879 1880 1881 1882
	pte_t *ptep, *ptem;

	ptem = ptep = pte_offset_map(&pmd, addr);
	do {
1883
		pte_t pte = gup_get_pte(ptep);
1884
		struct page *head, *page;
1885 1886 1887

		/*
		 * Similar to the PMD case below, NUMA hinting must take slow
1888
		 * path using the pte_protnone check.
1889
		 */
1890 1891 1892
		if (pte_protnone(pte))
			goto pte_unmap;

1893
		if (!pte_access_permitted(pte, flags & FOLL_WRITE))
1894 1895
			goto pte_unmap;

1896
		if (pte_devmap(pte)) {
1897 1898 1899
			if (unlikely(flags & FOLL_LONGTERM))
				goto pte_unmap;

1900 1901 1902 1903 1904 1905
			pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
			if (unlikely(!pgmap)) {
				undo_dev_pagemap(nr, nr_start, pages);
				goto pte_unmap;
			}
		} else if (pte_special(pte))
1906 1907 1908 1909 1910
			goto pte_unmap;

		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
		page = pte_page(pte);

1911 1912
		head = try_get_compound_head(page, 1);
		if (!head)
1913 1914 1915
			goto pte_unmap;

		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
1916
			put_page(head);
1917 1918 1919
			goto pte_unmap;
		}

1920
		VM_BUG_ON_PAGE(compound_head(page) != head, page);
1921 1922

		SetPageReferenced(page);
1923 1924 1925 1926 1927 1928 1929 1930
		pages[*nr] = page;
		(*nr)++;

	} while (ptep++, addr += PAGE_SIZE, addr != end);

	ret = 1;

pte_unmap:
1931 1932
	if (pgmap)
		put_dev_pagemap(pgmap);
1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947
	pte_unmap(ptem);
	return ret;
}
#else

/*
 * If we can't determine whether or not a pte is special, then fail immediately
 * for ptes. Note, we can still pin HugeTLB and THP as these are guaranteed not
 * to be special.
 *
 * For a futex to be placed on a THP tail page, get_futex_key requires a
 * __get_user_pages_fast implementation that can pin pages. Thus it's still
 * useful to have gup_huge_pmd even if we can't operate on ptes.
 */
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
1948
			 unsigned int flags, struct page **pages, int *nr)
1949 1950 1951
{
	return 0;
}
1952
#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
1953

R
Robin Murphy 已提交
1954
#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974
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);
		(*nr)++;
		pfn++;
	} while (addr += PAGE_SIZE, addr != end);
1975 1976 1977

	if (pgmap)
		put_dev_pagemap(pgmap);
1978 1979 1980
	return 1;
}

1981
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
1982 1983 1984
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;
1985 1986 1987 1988 1989
	int nr_start = *nr;

	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
		return 0;
1990

1991 1992 1993 1994 1995
	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
		undo_dev_pagemap(nr, nr_start, pages);
		return 0;
	}
	return 1;
1996 1997
}

1998
static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
1999 2000 2001
		unsigned long end, struct page **pages, int *nr)
{
	unsigned long fault_pfn;
2002 2003 2004 2005 2006
	int nr_start = *nr;

	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
	if (!__gup_device_huge(fault_pfn, addr, end, pages, nr))
		return 0;
2007

2008 2009 2010 2011 2012
	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
		undo_dev_pagemap(nr, nr_start, pages);
		return 0;
	}
	return 1;
2013 2014
}
#else
2015
static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2016 2017 2018 2019 2020 2021
		unsigned long end, struct page **pages, int *nr)
{
	BUILD_BUG();
	return 0;
}

2022
static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
2023 2024 2025 2026 2027 2028 2029
		unsigned long end, struct page **pages, int *nr)
{
	BUILD_BUG();
	return 0;
}
#endif

2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052
static int record_subpages(struct page *page, unsigned long addr,
			   unsigned long end, struct page **pages)
{
	int nr;

	for (nr = 0; addr != end; addr += PAGE_SIZE)
		pages[nr++] = page++;

	return nr;
}

static void put_compound_head(struct page *page, int refs)
{
	VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
	/*
	 * Calling put_page() for each ref is unnecessarily slow. Only the last
	 * ref needs a put_page().
	 */
	if (refs > 1)
		page_ref_sub(page, refs - 1);
	put_page(page);
}

2053 2054 2055 2056 2057 2058 2059 2060 2061
#ifdef CONFIG_ARCH_HAS_HUGEPD
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
				      unsigned long sz)
{
	unsigned long __boundary = (addr + sz) & ~(sz-1);
	return (__boundary - 1 < end - 1) ? __boundary : end;
}

static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
2062 2063
		       unsigned long end, unsigned int flags,
		       struct page **pages, int *nr)
2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075
{
	unsigned long pte_end;
	struct page *head, *page;
	pte_t pte;
	int refs;

	pte_end = (addr + sz) & ~(sz-1);
	if (pte_end < end)
		end = pte_end;

	pte = READ_ONCE(*ptep);

2076
	if (!pte_access_permitted(pte, flags & FOLL_WRITE))
2077 2078 2079 2080 2081 2082 2083
		return 0;

	/* hugepages are never "special" */
	VM_BUG_ON(!pfn_valid(pte_pfn(pte)));

	head = pte_page(pte);
	page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
2084
	refs = record_subpages(page, addr, end, pages + *nr);
2085

2086
	head = try_get_compound_head(head, refs);
2087
	if (!head)
2088 2089 2090
		return 0;

	if (unlikely(pte_val(pte) != pte_val(*ptep))) {
2091
		put_compound_head(head, refs);
2092 2093 2094
		return 0;
	}

2095
	*nr += refs;
2096
	SetPageReferenced(head);
2097 2098 2099 2100
	return 1;
}

static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2101
		unsigned int pdshift, unsigned long end, unsigned int flags,
2102 2103 2104 2105 2106 2107 2108 2109 2110
		struct page **pages, int *nr)
{
	pte_t *ptep;
	unsigned long sz = 1UL << hugepd_shift(hugepd);
	unsigned long next;

	ptep = hugepte_offset(hugepd, addr, pdshift);
	do {
		next = hugepte_addr_end(addr, end, sz);
2111
		if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
2112 2113 2114 2115 2116 2117 2118
			return 0;
	} while (ptep++, addr = next, addr != end);

	return 1;
}
#else
static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
2119
		unsigned int pdshift, unsigned long end, unsigned int flags,
2120 2121 2122 2123 2124 2125
		struct page **pages, int *nr)
{
	return 0;
}
#endif /* CONFIG_ARCH_HAS_HUGEPD */

2126
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
2127 2128
			unsigned long end, unsigned int flags,
			struct page **pages, int *nr)
2129
{
2130
	struct page *head, *page;
2131 2132
	int refs;

2133
	if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
2134 2135
		return 0;

2136 2137 2138
	if (pmd_devmap(orig)) {
		if (unlikely(flags & FOLL_LONGTERM))
			return 0;
2139
		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
2140
	}
2141

2142
	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
2143
	refs = record_subpages(page, addr, end, pages + *nr);
2144

2145
	head = try_get_compound_head(pmd_page(orig), refs);
2146
	if (!head)
2147 2148 2149
		return 0;

	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
2150
		put_compound_head(head, refs);
2151 2152 2153
		return 0;
	}

2154
	*nr += refs;
2155
	SetPageReferenced(head);
2156 2157 2158 2159
	return 1;
}

static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
2160
		unsigned long end, unsigned int flags, struct page **pages, int *nr)
2161
{
2162
	struct page *head, *page;
2163 2164
	int refs;

2165
	if (!pud_access_permitted(orig, flags & FOLL_WRITE))
2166 2167
		return 0;

2168 2169 2170
	if (pud_devmap(orig)) {
		if (unlikely(flags & FOLL_LONGTERM))
			return 0;
2171
		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
2172
	}
2173

2174
	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
2175
	refs = record_subpages(page, addr, end, pages + *nr);
2176

2177
	head = try_get_compound_head(pud_page(orig), refs);
2178
	if (!head)
2179 2180 2181
		return 0;

	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
2182
		put_compound_head(head, refs);
2183 2184 2185
		return 0;
	}

2186
	*nr += refs;
2187
	SetPageReferenced(head);
2188 2189 2190
	return 1;
}

2191
static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
2192
			unsigned long end, unsigned int flags,
2193 2194 2195
			struct page **pages, int *nr)
{
	int refs;
2196
	struct page *head, *page;
2197

2198
	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
2199 2200
		return 0;

2201
	BUILD_BUG_ON(pgd_devmap(orig));
2202

2203
	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
2204
	refs = record_subpages(page, addr, end, pages + *nr);
2205

2206
	head = try_get_compound_head(pgd_page(orig), refs);
2207
	if (!head)
2208 2209 2210
		return 0;

	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
2211
		put_compound_head(head, refs);
2212 2213 2214
		return 0;
	}

2215
	*nr += refs;
2216
	SetPageReferenced(head);
2217 2218 2219
	return 1;
}

2220
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
2221
		unsigned int flags, struct page **pages, int *nr)
2222 2223 2224 2225 2226 2227
{
	unsigned long next;
	pmd_t *pmdp;

	pmdp = pmd_offset(&pud, addr);
	do {
2228
		pmd_t pmd = READ_ONCE(*pmdp);
2229 2230

		next = pmd_addr_end(addr, end);
2231
		if (!pmd_present(pmd))
2232 2233
			return 0;

Y
Yu Zhao 已提交
2234 2235
		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
			     pmd_devmap(pmd))) {
2236 2237 2238 2239 2240
			/*
			 * NUMA hinting faults need to be handled in the GUP
			 * slowpath for accounting purposes and so that they
			 * can be serialised against THP migration.
			 */
2241
			if (pmd_protnone(pmd))
2242 2243
				return 0;

2244
			if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
2245 2246 2247
				pages, nr))
				return 0;

2248 2249 2250 2251 2252 2253
		} else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) {
			/*
			 * architecture have different format for hugetlbfs
			 * pmd format and THP pmd format
			 */
			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
2254
					 PMD_SHIFT, next, flags, pages, nr))
2255
				return 0;
2256
		} else if (!gup_pte_range(pmd, addr, next, flags, pages, nr))
2257
			return 0;
2258 2259 2260 2261 2262
	} while (pmdp++, addr = next, addr != end);

	return 1;
}

2263
static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
2264
			 unsigned int flags, struct page **pages, int *nr)
2265 2266 2267 2268
{
	unsigned long next;
	pud_t *pudp;

2269
	pudp = pud_offset(&p4d, addr);
2270
	do {
2271
		pud_t pud = READ_ONCE(*pudp);
2272 2273

		next = pud_addr_end(addr, end);
Q
Qiujun Huang 已提交
2274
		if (unlikely(!pud_present(pud)))
2275
			return 0;
2276
		if (unlikely(pud_huge(pud))) {
2277
			if (!gup_huge_pud(pud, pudp, addr, next, flags,
2278 2279 2280 2281
					  pages, nr))
				return 0;
		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
2282
					 PUD_SHIFT, next, flags, pages, nr))
2283
				return 0;
2284
		} else if (!gup_pmd_range(pud, addr, next, flags, pages, nr))
2285 2286 2287 2288 2289 2290
			return 0;
	} while (pudp++, addr = next, addr != end);

	return 1;
}

2291
static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
2292
			 unsigned int flags, struct page **pages, int *nr)
2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306
{
	unsigned long next;
	p4d_t *p4dp;

	p4dp = p4d_offset(&pgd, addr);
	do {
		p4d_t p4d = READ_ONCE(*p4dp);

		next = p4d_addr_end(addr, end);
		if (p4d_none(p4d))
			return 0;
		BUILD_BUG_ON(p4d_huge(p4d));
		if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
2307
					 P4D_SHIFT, next, flags, pages, nr))
2308
				return 0;
2309
		} else if (!gup_pud_range(p4d, addr, next, flags, pages, nr))
2310 2311 2312 2313 2314 2315
			return 0;
	} while (p4dp++, addr = next, addr != end);

	return 1;
}

2316
static void gup_pgd_range(unsigned long addr, unsigned long end,
2317
		unsigned int flags, struct page **pages, int *nr)
2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329
{
	unsigned long next;
	pgd_t *pgdp;

	pgdp = pgd_offset(current->mm, addr);
	do {
		pgd_t pgd = READ_ONCE(*pgdp);

		next = pgd_addr_end(addr, end);
		if (pgd_none(pgd))
			return;
		if (unlikely(pgd_huge(pgd))) {
2330
			if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
2331 2332 2333 2334
					  pages, nr))
				return;
		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
2335
					 PGDIR_SHIFT, next, flags, pages, nr))
2336
				return;
2337
		} else if (!gup_p4d_range(pgd, addr, next, flags, pages, nr))
2338 2339 2340
			return;
	} while (pgdp++, addr = next, addr != end);
}
2341 2342 2343 2344 2345 2346
#else
static inline void gup_pgd_range(unsigned long addr, unsigned long end,
		unsigned int flags, struct page **pages, int *nr)
{
}
#endif /* CONFIG_HAVE_FAST_GUP */
2347 2348 2349 2350 2351 2352

#ifndef gup_fast_permitted
/*
 * Check if it's allowed to use __get_user_pages_fast() for the range, or
 * we need to fall back to the slow version:
 */
2353
static bool gup_fast_permitted(unsigned long start, unsigned long end)
2354
{
2355
	return true;
2356 2357 2358
}
#endif

2359 2360
/*
 * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
2361 2362 2363
 * the regular GUP.
 * Note a difference with get_user_pages_fast: this always returns the
 * number of pages pinned, 0 if no pages were pinned.
2364 2365 2366
 *
 * If the architecture does not support this function, simply return with no
 * pages pinned.
2367 2368 2369 2370
 */
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
			  struct page **pages)
{
2371
	unsigned long len, end;
2372
	unsigned long flags;
2373 2374
	int nr = 0;

2375
	start = untagged_addr(start) & PAGE_MASK;
2376 2377 2378
	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;

2379 2380
	if (end <= start)
		return 0;
2381
	if (unlikely(!access_ok((void __user *)start, len)))
2382 2383 2384 2385 2386 2387 2388
		return 0;

	/*
	 * Disable interrupts.  We use the nested form as we can already have
	 * interrupts disabled by get_futex_key.
	 *
	 * With interrupts disabled, we block page table pages from being
2389 2390
	 * freed from under us. See struct mmu_table_batch comments in
	 * include/asm-generic/tlb.h for more details.
2391 2392 2393 2394 2395
	 *
	 * We do not adopt an rcu_read_lock(.) here as we also want to
	 * block IPIs that come from THPs splitting.
	 */

2396 2397
	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
	    gup_fast_permitted(start, end)) {
2398
		local_irq_save(flags);
2399
		gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr);
2400 2401
		local_irq_restore(flags);
	}
2402 2403 2404

	return nr;
}
2405
EXPORT_SYMBOL_GPL(__get_user_pages_fast);
2406

2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429
static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
				   unsigned int gup_flags, struct page **pages)
{
	int ret;

	/*
	 * FIXME: FOLL_LONGTERM does not work with
	 * get_user_pages_unlocked() (see comments in that function)
	 */
	if (gup_flags & FOLL_LONGTERM) {
		down_read(&current->mm->mmap_sem);
		ret = __gup_longterm_locked(current, current->mm,
					    start, nr_pages,
					    pages, NULL, gup_flags);
		up_read(&current->mm->mmap_sem);
	} else {
		ret = get_user_pages_unlocked(start, nr_pages,
					      pages, gup_flags);
	}

	return ret;
}

2430 2431 2432
static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
					unsigned int gup_flags,
					struct page **pages)
2433
{
2434
	unsigned long addr, len, end;
2435
	int nr = 0, ret = 0;
2436

2437
	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
2438
				       FOLL_FORCE | FOLL_PIN)))
2439 2440
		return -EINVAL;

2441
	start = untagged_addr(start) & PAGE_MASK;
2442 2443 2444 2445
	addr = start;
	len = (unsigned long) nr_pages << PAGE_SHIFT;
	end = start + len;

2446
	if (end <= start)
2447
		return 0;
2448
	if (unlikely(!access_ok((void __user *)start, len)))
2449
		return -EFAULT;
2450

2451 2452
	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
	    gup_fast_permitted(start, end)) {
2453
		local_irq_disable();
2454
		gup_pgd_range(addr, end, gup_flags, pages, &nr);
2455
		local_irq_enable();
2456 2457
		ret = nr;
	}
2458 2459 2460 2461 2462 2463

	if (nr < nr_pages) {
		/* Try to get the remaining pages with get_user_pages */
		start += nr << PAGE_SHIFT;
		pages += nr;

2464 2465
		ret = __gup_longterm_unlocked(start, nr_pages - nr,
					      gup_flags, pages);
2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477

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

	return ret;
}
2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506

/**
 * get_user_pages_fast() - pin user pages in memory
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @gup_flags:	flags modifying pin behaviour
 * @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,
			unsigned int gup_flags, struct page **pages)
{
	/*
	 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
	 * never directly by the caller, so enforce that:
	 */
	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
		return -EINVAL;

	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
2507
EXPORT_SYMBOL_GPL(get_user_pages_fast);
2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577

/**
 * pin_user_pages_fast() - pin user pages in memory without taking locks
 *
 * For now, this is a placeholder function, until various call sites are
 * converted to use the correct get_user_pages*() or pin_user_pages*() API. So,
 * this is identical to get_user_pages_fast().
 *
 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
 * is NOT intended for Case 2 (RDMA: long-term pins).
 */
int pin_user_pages_fast(unsigned long start, int nr_pages,
			unsigned int gup_flags, struct page **pages)
{
	/*
	 * This is a placeholder, until the pin functionality is activated.
	 * Until then, just behave like the corresponding get_user_pages*()
	 * routine.
	 */
	return get_user_pages_fast(start, nr_pages, gup_flags, pages);
}
EXPORT_SYMBOL_GPL(pin_user_pages_fast);

/**
 * pin_user_pages_remote() - pin pages of a remote process (task != current)
 *
 * For now, this is a placeholder function, until various call sites are
 * converted to use the correct get_user_pages*() or pin_user_pages*() API. So,
 * this is identical to get_user_pages_remote().
 *
 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
 * is NOT intended for Case 2 (RDMA: long-term pins).
 */
long pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
			   unsigned long start, unsigned long nr_pages,
			   unsigned int gup_flags, struct page **pages,
			   struct vm_area_struct **vmas, int *locked)
{
	/*
	 * This is a placeholder, until the pin functionality is activated.
	 * Until then, just behave like the corresponding get_user_pages*()
	 * routine.
	 */
	return get_user_pages_remote(tsk, mm, start, nr_pages, gup_flags, pages,
				     vmas, locked);
}
EXPORT_SYMBOL(pin_user_pages_remote);

/**
 * pin_user_pages() - pin user pages in memory for use by other devices
 *
 * For now, this is a placeholder function, until various call sites are
 * converted to use the correct get_user_pages*() or pin_user_pages*() API. So,
 * this is identical to get_user_pages().
 *
 * This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
 * is NOT intended for Case 2 (RDMA: long-term pins).
 */
long pin_user_pages(unsigned long start, unsigned long nr_pages,
		    unsigned int gup_flags, struct page **pages,
		    struct vm_area_struct **vmas)
{
	/*
	 * This is a placeholder, until the pin functionality is activated.
	 * Until then, just behave like the corresponding get_user_pages*()
	 * routine.
	 */
	return get_user_pages(start, nr_pages, gup_flags, pages, vmas);
}
EXPORT_SYMBOL(pin_user_pages);