mm: move get_user_pages()-related code to separate file (4bbd4c77) · Commits · 戴 / test

mm/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -3,7 +3,7 @@
		#

		mmu-y := nommu.o
		mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
		mmu-$(CONFIG_MMU) := fremap.o gup.o highmem.o madvise.o memory.o mincore.o \
		mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
		vmalloc.o pagewalk.o pgtable-generic.o

mm/gup.c

0 → 100644

+649 −0

Original line number	Diff line number	Diff line
		#include <linux/kernel.h>
		#include <linux/errno.h>
		#include <linux/err.h>
		#include <linux/spinlock.h>

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

		#include "internal.h"

		/**
		* 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
		* @page_mask: on output, *page_mask is set according to the size of the page
		*
		* @flags can have FOLL_ flags set, defined in <linux/mm.h>
		*
		* Returns the mapped (struct page *), %NULL if no mapping exists, or
		* an error pointer if there is a mapping to something not represented
		* by a page descriptor (see also vm_normal_page()).
		*/
		struct page follow_page_mask(struct vm_area_struct vma,
		unsigned long address, unsigned int flags,
		unsigned int *page_mask)
		{
		pgd_t *pgd;
		pud_t *pud;
		pmd_t *pmd;
		pte_t *ptep, pte;
		spinlock_t *ptl;
		struct page *page;
		struct mm_struct *mm = vma->vm_mm;

		*page_mask = 0;

		page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
		if (!IS_ERR(page)) {
		BUG_ON(flags & FOLL_GET);
		goto out;
		}

		page = NULL;
		pgd = pgd_offset(mm, address);
		if (pgd_none(pgd) \|\| unlikely(pgd_bad(pgd)))
		goto no_page_table;

		pud = pud_offset(pgd, address);
		if (pud_none(*pud))
		goto no_page_table;
		if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
		if (flags & FOLL_GET)
		goto out;
		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
		goto out;
		}
		if (unlikely(pud_bad(*pud)))
		goto no_page_table;

		pmd = pmd_offset(pud, address);
		if (pmd_none(*pmd))
		goto no_page_table;
		if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
		if (flags & FOLL_GET) {
		/*
		* Refcount on tail pages are not well-defined and
		* shouldn't be taken. The caller should handle a NULL
		* return when trying to follow tail pages.
		*/
		if (PageHead(page))
		get_page(page);
		else {
		page = NULL;
		goto out;
		}
		}
		goto out;
		}
		if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
		goto no_page_table;
		if (pmd_trans_huge(*pmd)) {
		if (flags & FOLL_SPLIT) {
		split_huge_page_pmd(vma, address, pmd);
		goto split_fallthrough;
		}
		ptl = pmd_lock(mm, pmd);
		if (likely(pmd_trans_huge(*pmd))) {
		if (unlikely(pmd_trans_splitting(*pmd))) {
		spin_unlock(ptl);
		wait_split_huge_page(vma->anon_vma, pmd);
		} else {
		page = follow_trans_huge_pmd(vma, address,
		pmd, flags);
		spin_unlock(ptl);
		*page_mask = HPAGE_PMD_NR - 1;
		goto out;
		}
		} else
		spin_unlock(ptl);
		/* fall through */
		}
		split_fallthrough:
		if (unlikely(pmd_bad(*pmd)))
		goto no_page_table;

		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;
		if (pte_none(pte) \|\| pte_file(pte))
		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);
		goto split_fallthrough;
		}
		if ((flags & FOLL_NUMA) && pte_numa(pte))
		goto no_page;
		if ((flags & FOLL_WRITE) && !pte_write(pte))
		goto unlock;

		page = vm_normal_page(vma, address, pte);
		if (unlikely(!page)) {
		if ((flags & FOLL_DUMP) \|\|
		!is_zero_pfn(pte_pfn(pte)))
		goto bad_page;
		page = pte_page(pte);
		}

		if (flags & FOLL_GET)
		get_page_foll(page);
		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);
		}
		if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
		/*
		* 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);
		}
		}
		unlock:
		pte_unmap_unlock(ptep, ptl);
		out:
		return page;

		bad_page:
		pte_unmap_unlock(ptep, ptl);
		return ERR_PTR(-EFAULT);

		no_page:
		pte_unmap_unlock(ptep, ptl);
		if (!pte_none(pte))
		return page;

		no_page_table:
		/*
		* 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 page;
		}

		static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
		{
		return stack_guard_page_start(vma, addr) \|\|
		stack_guard_page_end(vma, addr+PAGE_SIZE);
		}

		/**
		* __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
		*
		* 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. Each page returned must be released
		* with a put_page() call when it is finished with. vmas will only
		* remain valid while 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.
		*
		* 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,
		* *@nonblocking will be set to 0.
		*
		* 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.
		*/
		long __get_user_pages(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 nonblocking)
		{
		long i;
		unsigned long vm_flags;
		unsigned int page_mask;

		if (!nr_pages)
		return 0;

		VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));

		/*
		* 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;

		i = 0;

		do {
		struct vm_area_struct *vma;

		vma = find_extend_vma(mm, start);
		if (!vma && in_gate_area(mm, start)) {
		unsigned long pg = start & PAGE_MASK;
		pgd_t *pgd;
		pud_t *pud;
		pmd_t *pmd;
		pte_t *pte;

		/* user gate pages are read-only */
		if (gup_flags & FOLL_WRITE)
		goto efault;
		if (pg > TASK_SIZE)
		pgd = pgd_offset_k(pg);
		else
		pgd = pgd_offset_gate(mm, pg);
		BUG_ON(pgd_none(*pgd));
		pud = pud_offset(pgd, pg);
		BUG_ON(pud_none(*pud));
		pmd = pmd_offset(pud, pg);
		if (pmd_none(*pmd))
		goto efault;
		VM_BUG_ON(pmd_trans_huge(*pmd));
		pte = pte_offset_map(pmd, pg);
		if (pte_none(*pte)) {
		pte_unmap(pte);
		goto efault;
		}
		vma = get_gate_vma(mm);
		if (pages) {
		struct page *page;

		page = vm_normal_page(vma, start, *pte);
		if (!page) {
		if (!(gup_flags & FOLL_DUMP) &&
		is_zero_pfn(pte_pfn(*pte)))
		page = pte_page(*pte);
		else {
		pte_unmap(pte);
		goto efault;
		}
		}
		pages[i] = page;
		get_page(page);
		}
		pte_unmap(pte);
		page_mask = 0;
		goto next_page;
		}

		if (!vma)
		goto efault;
		vm_flags = vma->vm_flags;
		if (vm_flags & (VM_IO \| VM_PFNMAP))
		goto efault;

		if (gup_flags & FOLL_WRITE) {
		if (!(vm_flags & VM_WRITE)) {
		if (!(gup_flags & FOLL_FORCE))
		goto 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.
		*/
		if (!is_cow_mapping(vm_flags)) {
		WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
		goto efault;
		}
		}
		} else {
		if (!(vm_flags & VM_READ)) {
		if (!(gup_flags & FOLL_FORCE))
		goto efault;
		/*
		* Is there actually any vma we can reach here
		* which does not have VM_MAYREAD set?
		*/
		if (!(vm_flags & VM_MAYREAD))
		goto efault;
		}
		}

		if (is_vm_hugetlb_page(vma)) {
		i = follow_hugetlb_page(mm, vma, pages, vmas,
		&start, &nr_pages, i, gup_flags);
		continue;
		}

		do {
		struct page *page;
		unsigned int foll_flags = gup_flags;
		unsigned int page_increm;

		/*
		* If we have a pending SIGKILL, don't keep faulting
		* pages and potentially allocating memory.
		*/
		if (unlikely(fatal_signal_pending(current)))
		return i ? i : -ERESTARTSYS;

		cond_resched();
		while (!(page = follow_page_mask(vma, start,
		foll_flags, &page_mask))) {
		int ret;
		unsigned int fault_flags = 0;

		/* For mlock, just skip the stack guard page. */
		if (foll_flags & FOLL_MLOCK) {
		if (stack_guard_page(vma, start))
		goto next_page;
		}
		if (foll_flags & FOLL_WRITE)
		fault_flags \|= FAULT_FLAG_WRITE;
		if (nonblocking)
		fault_flags \|= FAULT_FLAG_ALLOW_RETRY;
		if (foll_flags & FOLL_NOWAIT)
		fault_flags \|= (FAULT_FLAG_ALLOW_RETRY \| FAULT_FLAG_RETRY_NOWAIT);

		ret = handle_mm_fault(mm, vma, start,
		fault_flags);

		if (ret & VM_FAULT_ERROR) {
		if (ret & VM_FAULT_OOM)
		return i ? i : -ENOMEM;
		if (ret & (VM_FAULT_HWPOISON \|
		VM_FAULT_HWPOISON_LARGE)) {
		if (i)
		return i;
		else if (gup_flags & FOLL_HWPOISON)
		return -EHWPOISON;
		else
		return -EFAULT;
		}
		if (ret & VM_FAULT_SIGBUS)
		goto efault;
		BUG();
		}

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

		if (ret & VM_FAULT_RETRY) {
		if (nonblocking)
		*nonblocking = 0;
		return i;
		}

		/*
		* 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))
		foll_flags &= ~FOLL_WRITE;

		cond_resched();
		}
		if (IS_ERR(page))
		return i ? i : PTR_ERR(page);
		if (pages) {
		pages[i] = page;

		flush_anon_page(vma, page, start);
		flush_dcache_page(page);
		page_mask = 0;
		}
		next_page:
		if (vmas) {
		vmas[i] = vma;
		page_mask = 0;
		}
		page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
		if (page_increm > nr_pages)
		page_increm = nr_pages;
		i += page_increm;
		start += page_increm * PAGE_SIZE;
		nr_pages -= page_increm;
		} while (nr_pages && start < vma->vm_end);
		} while (nr_pages);
		return i;
		efault:
		return i ? : -EFAULT;
		}
		EXPORT_SYMBOL(__get_user_pages);

		/*
		* 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()
		*
		* 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
		* handle_mm_fault() only guarantees to update these in the struct page.
		*
		* 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.
		*
		* This should be called with the mm_sem held for read.
		*/
		int fixup_user_fault(struct task_struct tsk, struct mm_struct mm,
		unsigned long address, unsigned int fault_flags)
		{
		struct vm_area_struct *vma;
		vm_flags_t vm_flags;
		int ret;

		vma = find_extend_vma(mm, address);
		if (!vma \|\| address < vma->vm_start)
		return -EFAULT;

		vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
		if (!(vm_flags & vma->vm_flags))
		return -EFAULT;

		ret = handle_mm_fault(mm, vma, address, fault_flags);
		if (ret & VM_FAULT_ERROR) {
		if (ret & VM_FAULT_OOM)
		return -ENOMEM;
		if (ret & (VM_FAULT_HWPOISON \| VM_FAULT_HWPOISON_LARGE))
		return -EHWPOISON;
		if (ret & VM_FAULT_SIGBUS)
		return -EFAULT;
		BUG();
		}
		if (tsk) {
		if (ret & VM_FAULT_MAJOR)
		tsk->maj_flt++;
		else
		tsk->min_flt++;
		}
		return 0;
		}

		/*
		* get_user_pages() - 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
		* @write: whether pages will be written to by the caller
		* @force: whether to force access even when user mapping is currently
		* protected (but never forces write access to shared mapping).
		* @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.
		*
		* 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. Each page returned must be released
		* with a put_page() call when it is finished with. vmas will only
		* remain valid while 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 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.
		*/
		long get_user_pages(struct task_struct tsk, struct mm_struct mm,
		unsigned long start, unsigned long nr_pages, int write,
		int force, struct page pages, struct vm_area_struct vmas)
		{
		int flags = FOLL_TOUCH;

		if (pages)
		flags \|= FOLL_GET;
		if (write)
		flags \|= FOLL_WRITE;
		if (force)
		flags \|= FOLL_FORCE;

		return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
		NULL);
		}
		EXPORT_SYMBOL(get_user_pages);

		/**
		* 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 page_cache_release() or 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 */

mm/internal.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -169,6 +169,11 @@ static inline unsigned long page_order(struct page *page)
		return page_private(page);
		}

		static inline bool is_cow_mapping(vm_flags_t flags)
		{
		return (flags & (VM_SHARED \| VM_MAYWRITE)) == VM_MAYWRITE;
		}

		/* mm/util.c */
		void __vma_link_list(struct mm_struct mm, struct vm_area_struct vma,
		struct vm_area_struct prev, struct rb_node rb_parent);

mm/memory.c

+0 −641

File changed.

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