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/backing-dev.h>
 #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 <linux/mmu_notifier.h>

 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>

 #include "internal.h"

 static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long addr, pte_t *ptep)
 {
 	pte_t pte = *ptep;

 	if (pte_present(pte)) {
 		struct page *page;

 		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);
 			update_hiwater_rss(mm);
 			dec_mm_counter(mm, MM_FILEPAGES);
 		}
 	} else {
 		if (!pte_file(pte))
 			free_swap_and_cache(pte_to_swp_entry(pte));
 		pte_clear_not_present_full(mm, addr, ptep, 0);
 	}
 }

 /*
  * Install a file pte to a given virtual memory address, release any
  * previously existing mapping.
  */
 static 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;
 	spinlock_t *ptl;

 	pte = get_locked_pte(mm, addr, &ptl);
 	if (!pte)
 		goto out;

 	if (!pte_none(*pte))
 		zap_pte(mm, vma, addr, pte);

 	set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
 	/*
 	 * 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;
 }

 static int populate_range(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long addr, unsigned long size, pgoff_t pgoff)
 {
 	int err;

 	do {
 		err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
 		if (err)
 			return err;

 		size -= PAGE_SIZE;
 		addr += PAGE_SIZE;
 		pgoff++;
 	} while (size);

         return 0;

 }

 /**
  * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
  * @start: start of the remapped virtual memory range
  * @size: size of the remapped virtual memory range
  * @prot: new protection bits of the range (see NOTE)
  * @pgoff: to-be-mapped page of the backing store file
  * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
  *
  * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
  * (shared backing store file).
  *
  * 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 (but must be zero),
  * and the vma's default protection is used. Arbitrary protections
  * might be implemented in the future.
  */
 SYSCALL_DEFINE5(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;
 	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;

 	/* Does pgoff wrap? */
 	if (pgoff + (size >> PAGE_SHIFT) < pgoff)
 		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))
 		goto out;

 	if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
 		goto out;

 	if (!(vma->vm_flags & VM_CAN_NONLINEAR))
 		goto out;

 	if (start < vma->vm_start || start + size > vma->vm_end)
 		goto out;

 	/* Must set VM_NONLINEAR before any pages are populated. */
 	if (!(vma->vm_flags & VM_NONLINEAR)) {
 		/* Don't need a nonlinear mapping, exit success */
 		if (pgoff == linear_page_index(vma, start)) {
 			err = 0;
 			goto out;
 		}

 		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;
 		/*
 		 * page_mkclean doesn't work on nonlinear vmas, so if
 		 * dirty pages need to be accounted, emulate with linear
 		 * vmas.
 		 */
 		if (mapping_cap_account_dirty(mapping)) {
 			unsigned long addr;
 			struct file *file = vma->vm_file;

 			flags &= MAP_NONBLOCK;
 			get_file(file);
 			addr = mmap_region(file, start, size,
 					flags, vma->vm_flags, pgoff);
 			fput(file);
 			if (IS_ERR_VALUE(addr)) {
 				err = addr;
 			} else {
 				BUG_ON(addr != start);
 				err = 0;
 			}
 			goto out;
 		}
 		mutex_lock(&mapping->i_mmap_mutex);
 		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);
 		mutex_unlock(&mapping->i_mmap_mutex);
 	}

 	if (vma->vm_flags & VM_LOCKED) {
 		/*
 		 * drop PG_Mlocked flag for over-mapped range
 		 */
 		unsigned int saved_flags = vma->vm_flags;
 		munlock_vma_pages_range(vma, start, start + size);
 		vma->vm_flags = saved_flags;
 	}

 	mmu_notifier_invalidate_range_start(mm, start, start + size);
 	err = populate_range(mm, vma, start, size, pgoff);
 	mmu_notifier_invalidate_range_end(mm, start, start + size);
 	if (!err && !(flags & MAP_NONBLOCK)) {
 		if (vma->vm_flags & VM_LOCKED) {
 			/*
 			 * might be mapping previously unmapped range of file
 			 */
 			mlock_vma_pages_range(vma, start, start + size);
 		} else {
 			if (unlikely(has_write_lock)) {
 				downgrade_write(&mm->mmap_sem);
 				has_write_lock = 0;
 			}
 			make_pages_present(start, start+size);
 		}
 	}

 	/*
 	 * 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).
 	 */

 out:
 	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/backing-dev.h>
	#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 <linux/mmu_notifier.h>

	#include <asm/mmu_context.h>
	#include <asm/cacheflush.h>
	#include <asm/tlbflush.h>

	#include "internal.h"

	static void zap_pte(struct mm_struct mm, struct vm_area_struct vma,
	unsigned long addr, pte_t *ptep)
	{
	pte_t pte = *ptep;

	if (pte_present(pte)) {
	struct page *page;

	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);
	update_hiwater_rss(mm);
	dec_mm_counter(mm, MM_FILEPAGES);
	}
	} else {
	if (!pte_file(pte))
	free_swap_and_cache(pte_to_swp_entry(pte));
	pte_clear_not_present_full(mm, addr, ptep, 0);
	}
	}

	/*
	* Install a file pte to a given virtual memory address, release any
	* previously existing mapping.
	*/
	static 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;
	spinlock_t *ptl;

	pte = get_locked_pte(mm, addr, &ptl);
	if (!pte)
	goto out;

	if (!pte_none(*pte))
	zap_pte(mm, vma, addr, pte);

	set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
	/*
	* 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;
	}

	static int populate_range(struct mm_struct mm, struct vm_area_struct vma,
	unsigned long addr, unsigned long size, pgoff_t pgoff)
	{
	int err;

	do {
	err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot);
	if (err)
	return err;

	size -= PAGE_SIZE;
	addr += PAGE_SIZE;
	pgoff++;
	} while (size);

	return 0;

	}

	/**
	* sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma
	* @start: start of the remapped virtual memory range
	* @size: size of the remapped virtual memory range
	* @prot: new protection bits of the range (see NOTE)
	* @pgoff: to-be-mapped page of the backing store file
	* @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
	*
	* sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma
	* (shared backing store file).
	*
	* 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 (but must be zero),
	* and the vma's default protection is used. Arbitrary protections
	* might be implemented in the future.
	*/
	SYSCALL_DEFINE5(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;
	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;

	/* Does pgoff wrap? */
	if (pgoff + (size >> PAGE_SHIFT) < pgoff)
	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))
	goto out;

	if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
	goto out;

	if (!(vma->vm_flags & VM_CAN_NONLINEAR))
	goto out;

	if (start < vma->vm_start \|\| start + size > vma->vm_end)
	goto out;

	/* Must set VM_NONLINEAR before any pages are populated. */
	if (!(vma->vm_flags & VM_NONLINEAR)) {
	/* Don't need a nonlinear mapping, exit success */
	if (pgoff == linear_page_index(vma, start)) {
	err = 0;
	goto out;
	}

	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;
	/*
	* page_mkclean doesn't work on nonlinear vmas, so if
	* dirty pages need to be accounted, emulate with linear
	* vmas.
	*/
	if (mapping_cap_account_dirty(mapping)) {
	unsigned long addr;
	struct file *file = vma->vm_file;

	flags &= MAP_NONBLOCK;
	get_file(file);
	addr = mmap_region(file, start, size,
	flags, vma->vm_flags, pgoff);
	fput(file);
	if (IS_ERR_VALUE(addr)) {
	err = addr;
	} else {
	BUG_ON(addr != start);
	err = 0;
	}
	goto out;
	}
	mutex_lock(&mapping->i_mmap_mutex);
	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);
	mutex_unlock(&mapping->i_mmap_mutex);
	}

	if (vma->vm_flags & VM_LOCKED) {
	/*
	* drop PG_Mlocked flag for over-mapped range
	*/
	unsigned int saved_flags = vma->vm_flags;
	munlock_vma_pages_range(vma, start, start + size);
	vma->vm_flags = saved_flags;
	}

	mmu_notifier_invalidate_range_start(mm, start, start + size);
	err = populate_range(mm, vma, start, size, pgoff);
	mmu_notifier_invalidate_range_end(mm, start, start + size);
	if (!err && !(flags & MAP_NONBLOCK)) {
	if (vma->vm_flags & VM_LOCKED) {
	/*
	* might be mapping previously unmapped range of file
	*/
	mlock_vma_pages_range(vma, start, start + size);
	} else {
	if (unlikely(has_write_lock)) {
	downgrade_write(&mm->mmap_sem);
	has_write_lock = 0;
	}
	make_pages_present(start, start+size);
	}
	}

	/*
	* 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).
	*/

	out:
	if (likely(!has_write_lock))
	up_read(&mm->mmap_sem);
	else
	up_write(&mm->mmap_sem);

	return err;
	}