229 lines
6.1 KiB
C
229 lines
6.1 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/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/module.h>
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#include <linux/syscalls.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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static int 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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struct page *page = NULL;
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if (pte_present(pte)) {
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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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}
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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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return !!page;
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}
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/*
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* Install a file page to a given virtual memory address, release any
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* previously existing mapping.
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*/
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int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
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unsigned long addr, struct page *page, pgprot_t prot)
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{
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struct inode *inode;
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pgoff_t size;
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int err = -ENOMEM;
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pte_t *pte;
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pte_t pte_val;
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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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/*
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* This page may have been truncated. Tell the
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* caller about it.
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*/
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err = -EINVAL;
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inode = vma->vm_file->f_mapping->host;
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size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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if (!page->mapping || page->index >= size)
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goto unlock;
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err = -ENOMEM;
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if (page_mapcount(page) > INT_MAX/2)
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goto unlock;
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if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
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inc_mm_counter(mm, file_rss);
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flush_icache_page(vma, page);
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pte_val = mk_pte(page, prot);
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set_pte_at(mm, addr, pte, pte_val);
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page_add_file_rmap(page);
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update_mmu_cache(vma, addr, pte_val);
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lazy_mmu_prot_update(pte_val);
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err = 0;
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unlock:
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pte_unmap_unlock(pte, ptl);
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out:
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return err;
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}
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EXPORT_SYMBOL(install_page);
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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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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) && zap_pte(mm, vma, addr, pte)) {
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update_hiwater_rss(mm);
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dec_mm_counter(mm, file_rss);
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}
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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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/***
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* sys_remap_file_pages - remap arbitrary pages of a shared backing store
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* file within an existing 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
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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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* 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, and the vma's default
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* protection is used. Arbitrary protections might be implemented in the
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* future.
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*/
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asmlinkage long sys_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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unsigned long end = start + size;
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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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/* 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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(!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) &&
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vma->vm_ops && vma->vm_ops->populate &&
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end > start && start >= vma->vm_start &&
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end <= vma->vm_end) {
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/* Must set VM_NONLINEAR before any pages are populated. */
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if (pgoff != linear_page_index(vma, start) &&
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!(vma->vm_flags & VM_NONLINEAR)) {
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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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spin_lock(&mapping->i_mmap_lock);
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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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spin_unlock(&mapping->i_mmap_lock);
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}
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err = vma->vm_ops->populate(vma, start, size,
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vma->vm_page_prot,
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pgoff, flags & MAP_NONBLOCK);
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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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}
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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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