/*
* 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 int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{
pte_t pte = *ptep;
struct page *page = NULL;
if (pte_present(pte)) {
flush_cache_page(vma, addr, pte_pfn(pte));
pte = ptep_clear_flush(vma, addr, ptep);
page = vm_normal_page(vma, addr, pte);
if (page) {
if (pte_dirty(pte))
set_page_dirty(page);
page_remove_rmap(page);
page_cache_release(page);
}
} else {
if (!pte_file(pte))
free_swap_and_cache(pte_to_swp_entry(pte));
pte_clear(mm, addr, ptep);
}
return !!page;
}
/*
* 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;
pte_t pte_val;
spinlock_t *ptl;
pte = get_locked_pte(mm, addr, &ptl);
if (!pte)
goto out;
/*
* 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 unlock;
err = -ENOMEM;
if (page_mapcount(page) > INT_MAX/2)
goto unlock;
if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
inc_mm_counter(mm, file_rss);
flush_icache_page(vma, page);
set_pte_at(mm, addr, pte, mk_pte(page, prot));
page_add_file_rmap(page);
pte_val = *pte;
update_mmu_cache(vma, addr, pte_val);
lazy_mmu_prot_update(pte_val);
err = 0;
unlock:
pte_unmap_unlock(pte, ptl);
out:
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;
pte_t pte_val;
spinlock_t *ptl;
pte = get_locked_pte(mm, addr, &ptl);
if (!pte)
goto out;
if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
update_hiwater_rss(mm);
dec_mm_counter(mm, file_rss);
}
set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
pte_val = *pte;
/*
* We don't need to run update_mmu_cache() here because the "file pte"
* being installed by install_file_pte() is not a real pte - it's a
* non-present entry (like a swap entry), noting what file offset should
* be mapped there when there's a fault (in a non-linear vma where
* that's not obvious).
*/
pte_unmap_unlock(pte, ptl);
err = 0;
out:
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.
*/
if (vma && (vma->vm_flags & VM_SHARED) &&
(!vma->vm_private_data || (vma->vm_flags & VM_NONLINEAR)) &&
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;
}
