diff options
Diffstat (limited to 'mm/fremap.c')
| -rw-r--r-- | mm/fremap.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/mm/fremap.c b/mm/fremap.c new file mode 100644 index 000000000000..3235fb77c133 --- /dev/null +++ b/mm/fremap.c @@ -0,0 +1,256 @@ +/* + * linux/mm/fremap.c + * + * Explicit pagetable population and nonlinear (random) mappings support. + * + * started by Ingo Molnar, Copyright (C) 2002, 2003 + */ + +#include <linux/mm.h> +#include <linux/swap.h> +#include <linux/file.h> +#include <linux/mman.h> +#include <linux/pagemap.h> +#include <linux/swapops.h> +#include <linux/rmap.h> +#include <linux/module.h> +#include <linux/syscalls.h> + +#include <asm/mmu_context.h> +#include <asm/cacheflush.h> +#include <asm/tlbflush.h> + +static inline void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep) +{ + pte_t pte = *ptep; + + if (pte_none(pte)) + return; + if (pte_present(pte)) { + unsigned long pfn = pte_pfn(pte); + + flush_cache_page(vma, addr, pfn); + pte = ptep_clear_flush(vma, addr, ptep); + if (pfn_valid(pfn)) { + struct page *page = pfn_to_page(pfn); + if (!PageReserved(page)) { + if (pte_dirty(pte)) + set_page_dirty(page); + page_remove_rmap(page); + page_cache_release(page); + dec_mm_counter(mm, rss); + } + } + } else { + if (!pte_file(pte)) + free_swap_and_cache(pte_to_swp_entry(pte)); + pte_clear(mm, addr, ptep); + } +} + +/* + * Install a file page to a given virtual memory address, release any + * previously existing mapping. + */ +int install_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr, struct page *page, pgprot_t prot) +{ + struct inode *inode; + pgoff_t size; + int err = -ENOMEM; + pte_t *pte; + pmd_t *pmd; + pud_t *pud; + pgd_t *pgd; + pte_t pte_val; + + pgd = pgd_offset(mm, addr); + spin_lock(&mm->page_table_lock); + + pud = pud_alloc(mm, pgd, addr); + if (!pud) + goto err_unlock; + + pmd = pmd_alloc(mm, pud, addr); + if (!pmd) + goto err_unlock; + + pte = pte_alloc_map(mm, pmd, addr); + if (!pte) + goto err_unlock; + + /* + * This page may have been truncated. Tell the + * caller about it. + */ + err = -EINVAL; + inode = vma->vm_file->f_mapping->host; + size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; + if (!page->mapping || page->index >= size) + goto err_unlock; + + zap_pte(mm, vma, addr, pte); + + inc_mm_counter(mm,rss); + flush_icache_page(vma, page); + set_pte_at(mm, addr, pte, mk_pte(page, prot)); + page_add_file_rmap(page); + pte_val = *pte; + pte_unmap(pte); + update_mmu_cache(vma, addr, pte_val); + + err = 0; +err_unlock: + spin_unlock(&mm->page_table_lock); + return err; +} +EXPORT_SYMBOL(install_page); + + +/* + * Install a file pte to a given virtual memory address, release any + * previously existing mapping. + */ +int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr, unsigned long pgoff, pgprot_t prot) +{ + int err = -ENOMEM; + pte_t *pte; + pmd_t *pmd; + pud_t *pud; + pgd_t *pgd; + pte_t pte_val; + + pgd = pgd_offset(mm, addr); + spin_lock(&mm->page_table_lock); + + pud = pud_alloc(mm, pgd, addr); + if (!pud) + goto err_unlock; + + pmd = pmd_alloc(mm, pud, addr); + if (!pmd) + goto err_unlock; + + pte = pte_alloc_map(mm, pmd, addr); + if (!pte) + goto err_unlock; + + zap_pte(mm, vma, addr, pte); + + set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff)); + pte_val = *pte; + pte_unmap(pte); + update_mmu_cache(vma, addr, pte_val); + spin_unlock(&mm->page_table_lock); + return 0; + +err_unlock: + spin_unlock(&mm->page_table_lock); + return err; +} + + +/*** + * sys_remap_file_pages - remap arbitrary pages of a shared backing store + * file within an existing vma. + * @start: start of the remapped virtual memory range + * @size: size of the remapped virtual memory range + * @prot: new protection bits of the range + * @pgoff: to be mapped page of the backing store file + * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. + * + * this syscall works purely via pagetables, so it's the most efficient + * way to map the same (large) file into a given virtual window. Unlike + * mmap()/mremap() it does not create any new vmas. The new mappings are + * also safe across swapout. + * + * NOTE: the 'prot' parameter right now is ignored, and the vma's default + * protection is used. Arbitrary protections might be implemented in the + * future. + */ +asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, + unsigned long __prot, unsigned long pgoff, unsigned long flags) +{ + struct mm_struct *mm = current->mm; + struct address_space *mapping; + unsigned long end = start + size; + struct vm_area_struct *vma; + int err = -EINVAL; + int has_write_lock = 0; + + if (__prot) + return err; + /* + * Sanitize the syscall parameters: + */ + start = start & PAGE_MASK; + size = size & PAGE_MASK; + + /* Does the address range wrap, or is the span zero-sized? */ + if (start + size <= start) + return err; + + /* Can we represent this offset inside this architecture's pte's? */ +#if PTE_FILE_MAX_BITS < BITS_PER_LONG + if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) + return err; +#endif + + /* We need down_write() to change vma->vm_flags. */ + down_read(&mm->mmap_sem); + retry: + vma = find_vma(mm, start); + + /* + * Make sure the vma is shared, that it supports prefaulting, + * and that the remapped range is valid and fully within + * the single existing vma. vm_private_data is used as a + * swapout cursor in a VM_NONLINEAR vma (unless VM_RESERVED + * or VM_LOCKED, but VM_LOCKED could be revoked later on). + */ + if (vma && (vma->vm_flags & VM_SHARED) && + (!vma->vm_private_data || + (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) && + vma->vm_ops && vma->vm_ops->populate && + end > start && start >= vma->vm_start && + end <= vma->vm_end) { + + /* Must set VM_NONLINEAR before any pages are populated. */ + if (pgoff != linear_page_index(vma, start) && + !(vma->vm_flags & VM_NONLINEAR)) { + if (!has_write_lock) { + up_read(&mm->mmap_sem); + down_write(&mm->mmap_sem); + has_write_lock = 1; + goto retry; + } + mapping = vma->vm_file->f_mapping; + spin_lock(&mapping->i_mmap_lock); + flush_dcache_mmap_lock(mapping); + vma->vm_flags |= VM_NONLINEAR; + vma_prio_tree_remove(vma, &mapping->i_mmap); + vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); + flush_dcache_mmap_unlock(mapping); + spin_unlock(&mapping->i_mmap_lock); + } + + err = vma->vm_ops->populate(vma, start, size, + vma->vm_page_prot, + pgoff, flags & MAP_NONBLOCK); + + /* + * We can't clear VM_NONLINEAR because we'd have to do + * it after ->populate completes, and that would prevent + * downgrading the lock. (Locks can't be upgraded). + */ + } + if (likely(!has_write_lock)) + up_read(&mm->mmap_sem); + else + up_write(&mm->mmap_sem); + + return err; +} + |