mm/fremap.c - kernel/msm - Gitiles

 /*
  *   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;
 }
	/*
	* 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;
	}