261 lines
6.7 KiB
C
261 lines
6.7 KiB
C
/*
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* linux/mm/fremap.c
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*
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* Explicit pagetable population and nonlinear (random) mappings support.
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*
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* started by Ingo Molnar, Copyright (C) 2002, 2003
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*/
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#include <linux/backing-dev.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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#include <linux/file.h>
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/swapops.h>
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#include <linux/rmap.h>
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#include <linux/syscalls.h>
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#include <linux/mmu_notifier.h>
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#include <asm/mmu_context.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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#include "internal.h"
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static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
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unsigned long addr, pte_t *ptep)
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{
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pte_t pte = *ptep;
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if (pte_present(pte)) {
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struct page *page;
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flush_cache_page(vma, addr, pte_pfn(pte));
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pte = ptep_clear_flush(vma, addr, ptep);
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page = vm_normal_page(vma, addr, pte);
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if (page) {
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if (pte_dirty(pte))
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set_page_dirty(page);
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page_remove_rmap(page);
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page_cache_release(page);
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update_hiwater_rss(mm);
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dec_mm_counter(mm, MM_FILEPAGES);
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}
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} else {
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if (!pte_file(pte))
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free_swap_and_cache(pte_to_swp_entry(pte));
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pte_clear_not_present_full(mm, addr, ptep, 0);
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}
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}
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/*
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* Install a file pte to a given virtual memory address, release any
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* previously existing mapping.
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*/
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static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
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unsigned long addr, unsigned long pgoff, pgprot_t prot)
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{
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int err = -ENOMEM;
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pte_t *pte;
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spinlock_t *ptl;
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pte = get_locked_pte(mm, addr, &ptl);
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if (!pte)
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goto out;
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if (!pte_none(*pte))
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zap_pte(mm, vma, addr, pte);
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set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
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/*
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* We don't need to run update_mmu_cache() here because the "file pte"
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* being installed by install_file_pte() is not a real pte - it's a
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* non-present entry (like a swap entry), noting what file offset should
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* be mapped there when there's a fault (in a non-linear vma where
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* that's not obvious).
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*/
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pte_unmap_unlock(pte, ptl);
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err = 0;
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out:
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return err;
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}
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static int populate_range(struct mm_struct *mm, struct vm_area_struct *vma,
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unsigned long addr, unsigned long size, pgoff_t pgoff)
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{
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int err;
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do {
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err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
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if (err)
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return err;
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size -= PAGE_SIZE;
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addr += PAGE_SIZE;
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pgoff++;
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} while (size);
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return 0;
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}
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/**
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* sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
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* @start: start of the remapped virtual memory range
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* @size: size of the remapped virtual memory range
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* @prot: new protection bits of the range (see NOTE)
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* @pgoff: to-be-mapped page of the backing store file
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* @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
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*
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* sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
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* (shared backing store file).
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*
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* This syscall works purely via pagetables, so it's the most efficient
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* way to map the same (large) file into a given virtual window. Unlike
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* mmap()/mremap() it does not create any new vmas. The new mappings are
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* also safe across swapout.
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*
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* NOTE: the @prot parameter right now is ignored (but must be zero),
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* and the vma's default protection is used. Arbitrary protections
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* might be implemented in the future.
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*/
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SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
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unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
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{
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struct mm_struct *mm = current->mm;
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struct address_space *mapping;
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struct vm_area_struct *vma;
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int err = -EINVAL;
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int has_write_lock = 0;
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if (prot)
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return err;
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/*
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* Sanitize the syscall parameters:
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*/
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start = start & PAGE_MASK;
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size = size & PAGE_MASK;
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/* Does the address range wrap, or is the span zero-sized? */
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if (start + size <= start)
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return err;
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/* Does pgoff wrap? */
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if (pgoff + (size >> PAGE_SHIFT) < pgoff)
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return err;
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/* Can we represent this offset inside this architecture's pte's? */
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#if PTE_FILE_MAX_BITS < BITS_PER_LONG
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if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
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return err;
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#endif
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/* We need down_write() to change vma->vm_flags. */
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down_read(&mm->mmap_sem);
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retry:
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vma = find_vma(mm, start);
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/*
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* Make sure the vma is shared, that it supports prefaulting,
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* and that the remapped range is valid and fully within
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* the single existing vma. vm_private_data is used as a
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* swapout cursor in a VM_NONLINEAR vma.
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*/
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if (!vma || !(vma->vm_flags & VM_SHARED))
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goto out;
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if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
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goto out;
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if (!(vma->vm_flags & VM_CAN_NONLINEAR))
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goto out;
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if (start < vma->vm_start || start + size > vma->vm_end)
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goto out;
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/* Must set VM_NONLINEAR before any pages are populated. */
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if (!(vma->vm_flags & VM_NONLINEAR)) {
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/* Don't need a nonlinear mapping, exit success */
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if (pgoff == linear_page_index(vma, start)) {
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err = 0;
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goto out;
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}
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if (!has_write_lock) {
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up_read(&mm->mmap_sem);
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down_write(&mm->mmap_sem);
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has_write_lock = 1;
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goto retry;
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}
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mapping = vma->vm_file->f_mapping;
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/*
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* page_mkclean doesn't work on nonlinear vmas, so if
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* dirty pages need to be accounted, emulate with linear
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* vmas.
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*/
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if (mapping_cap_account_dirty(mapping)) {
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unsigned long addr;
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struct file *file = get_file(vma->vm_file);
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flags &= MAP_NONBLOCK;
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addr = mmap_region(file, start, size,
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flags, vma->vm_flags, pgoff);
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fput(file);
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if (IS_ERR_VALUE(addr)) {
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err = addr;
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} else {
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BUG_ON(addr != start);
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err = 0;
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}
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goto out;
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}
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mutex_lock(&mapping->i_mmap_mutex);
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flush_dcache_mmap_lock(mapping);
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vma->vm_flags |= VM_NONLINEAR;
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vma_prio_tree_remove(vma, &mapping->i_mmap);
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vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
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flush_dcache_mmap_unlock(mapping);
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mutex_unlock(&mapping->i_mmap_mutex);
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}
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if (vma->vm_flags & VM_LOCKED) {
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/*
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* drop PG_Mlocked flag for over-mapped range
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*/
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vm_flags_t saved_flags = vma->vm_flags;
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munlock_vma_pages_range(vma, start, start + size);
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vma->vm_flags = saved_flags;
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}
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mmu_notifier_invalidate_range_start(mm, start, start + size);
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err = populate_range(mm, vma, start, size, pgoff);
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mmu_notifier_invalidate_range_end(mm, start, start + size);
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if (!err && !(flags & MAP_NONBLOCK)) {
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if (vma->vm_flags & VM_LOCKED) {
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/*
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* might be mapping previously unmapped range of file
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*/
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mlock_vma_pages_range(vma, start, start + size);
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} else {
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if (unlikely(has_write_lock)) {
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downgrade_write(&mm->mmap_sem);
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has_write_lock = 0;
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}
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make_pages_present(start, start+size);
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}
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}
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/*
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* We can't clear VM_NONLINEAR because we'd have to do
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* it after ->populate completes, and that would prevent
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* downgrading the lock. (Locks can't be upgraded).
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*/
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out:
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if (likely(!has_write_lock))
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up_read(&mm->mmap_sem);
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else
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up_write(&mm->mmap_sem);
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return err;
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}
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