mm/mremap.c - kernel/msm - Gitiles

 /*
  *	mm/mremap.c
  *
  *	(C) Copyright 1996 Linus Torvalds
  *
  *	Address space accounting code	<alan@lxorguk.ukuu.org.uk>
  *	(C) Copyright 2002 Red Hat Inc, All Rights Reserved
  */

 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <linux/shm.h>
 #include <linux/ksm.h>
 #include <linux/mman.h>
 #include <linux/swap.h>
 #include <linux/capability.h>
 #include <linux/fs.h>
 #include <linux/highmem.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/mmu_notifier.h>

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

 #include "internal.h"

 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;

 	pgd = pgd_offset(mm, addr);
 	if (pgd_none_or_clear_bad(pgd))
 		return NULL;

 	pud = pud_offset(pgd, addr);
 	if (pud_none_or_clear_bad(pud))
 		return NULL;

 	pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd))
 		return NULL;

 	return pmd;
 }

 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 			    unsigned long addr)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;

 	pgd = pgd_offset(mm, addr);
 	pud = pud_alloc(mm, pgd, addr);
 	if (!pud)
 		return NULL;

 	pmd = pmd_alloc(mm, pud, addr);
 	if (!pmd)
 		return NULL;

 	VM_BUG_ON(pmd_trans_huge(*pmd));

 	return pmd;
 }

 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 		unsigned long old_addr, unsigned long old_end,
 		struct vm_area_struct *new_vma, pmd_t *new_pmd,
 		unsigned long new_addr)
 {
 	struct address_space *mapping = NULL;
 	struct mm_struct *mm = vma->vm_mm;
 	pte_t *old_pte, *new_pte, pte;
 	spinlock_t *old_ptl, *new_ptl;
 	bool force_flush = false;
 	unsigned long len = old_end - old_addr;

 	if (vma->vm_file) {
 		/*
 		 * Subtle point from Rajesh Venkatasubramanian: before
 		 * moving file-based ptes, we must lock truncate_pagecache
 		 * out, since it might clean the dst vma before the src vma,
 		 * and we propagate stale pages into the dst afterward.
 		 */
 		mapping = vma->vm_file->f_mapping;
 		mutex_lock(&mapping->i_mmap_mutex);
 	}

 	/*
 	 * We don't have to worry about the ordering of src and dst
 	 * pte locks because exclusive mmap_sem prevents deadlock.
 	 */
 	old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
 	new_pte = pte_offset_map(new_pmd, new_addr);
 	new_ptl = pte_lockptr(mm, new_pmd);
 	if (new_ptl != old_ptl)
 		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
 	arch_enter_lazy_mmu_mode();

 	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
 				   new_pte++, new_addr += PAGE_SIZE) {
 		if (pte_none(*old_pte))
 			continue;
 		pte = ptep_get_and_clear(mm, old_addr, old_pte);
 		/*
 		 * If we are remapping a valid PTE, make sure
 		 * to flush TLB before we drop the PTL for the PTE.
 		 *
 		 * NOTE! Both old and new PTL matter: the old one
 		 * for racing with page_mkclean(), the new one to
 		 * make sure the physical page stays valid until
 		 * the TLB entry for the old mapping has been
 		 * flushed.
 		 */
 		if (pte_present(pte))
 			force_flush = true;
 		pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
 		set_pte_at(mm, new_addr, new_pte, pte);
 	}

 	arch_leave_lazy_mmu_mode();
 	if (force_flush)
 		flush_tlb_range(vma, old_end - len, old_end);
 	if (new_ptl != old_ptl)
 		spin_unlock(new_ptl);
 	pte_unmap(new_pte - 1);
 	pte_unmap_unlock(old_pte - 1, old_ptl);
 	if (mapping)
 		mutex_unlock(&mapping->i_mmap_mutex);
 }

 #define LATENCY_LIMIT	(64 * PAGE_SIZE)

 unsigned long move_page_tables(struct vm_area_struct *vma,
 		unsigned long old_addr, struct vm_area_struct *new_vma,
 		unsigned long new_addr, unsigned long len)
 {
 	unsigned long extent, next, old_end;
 	pmd_t *old_pmd, *new_pmd;

 	old_end = old_addr + len;
 	flush_cache_range(vma, old_addr, old_end);

 	mmu_notifier_invalidate_range_start(vma->vm_mm, old_addr, old_end);

 	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
 		cond_resched();
 		next = (old_addr + PMD_SIZE) & PMD_MASK;
 		/* even if next overflowed, extent below will be ok */
 		extent = next - old_addr;
 		if (extent > old_end - old_addr)
 			extent = old_end - old_addr;
 		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
 		if (!old_pmd)
 			continue;
 		new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 		if (!new_pmd)
 			break;
 		if (pmd_trans_huge(*old_pmd)) {
 			int err = 0;
 			if (extent == HPAGE_PMD_SIZE)
 				err = move_huge_pmd(vma, new_vma, old_addr,
 						    new_addr, old_end,
 						    old_pmd, new_pmd);
 			if (err > 0) {
 				continue;
 			} else if (!err) {
 				split_huge_page_pmd(vma->vm_mm, old_pmd);
 			}
 			VM_BUG_ON(pmd_trans_huge(*old_pmd));
 		}
 		if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
 						      new_pmd, new_addr))
 			break;
 		next = (new_addr + PMD_SIZE) & PMD_MASK;
 		if (extent > next - new_addr)
 			extent = next - new_addr;
 		if (extent > LATENCY_LIMIT)
 			extent = LATENCY_LIMIT;
 		move_ptes(vma, old_pmd, old_addr, old_addr + extent,
 				new_vma, new_pmd, new_addr);
 	}

 	mmu_notifier_invalidate_range_end(vma->vm_mm, old_end-len, old_end);

 	return len + old_addr - old_end;	/* how much done */
 }

 static unsigned long move_vma(struct vm_area_struct *vma,
 		unsigned long old_addr, unsigned long old_len,
 		unsigned long new_len, unsigned long new_addr)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct vm_area_struct *new_vma;
 	unsigned long vm_flags = vma->vm_flags;
 	unsigned long new_pgoff;
 	unsigned long moved_len;
 	unsigned long excess = 0;
 	unsigned long hiwater_vm;
 	int split = 0;
 	int err;

 	/*
 	 * We'd prefer to avoid failure later on in do_munmap:
 	 * which may split one vma into three before unmapping.
 	 */
 	if (mm->map_count >= sysctl_max_map_count - 3)
 		return -ENOMEM;

 	/*
 	 * Advise KSM to break any KSM pages in the area to be moved:
 	 * it would be confusing if they were to turn up at the new
 	 * location, where they happen to coincide with different KSM
 	 * pages recently unmapped.  But leave vma->vm_flags as it was,
 	 * so KSM can come around to merge on vma and new_vma afterwards.
 	 */
 	err = ksm_madvise(vma, old_addr, old_addr + old_len,
 						MADV_UNMERGEABLE, &vm_flags);
 	if (err)
 		return err;

 	new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
 	new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
 	if (!new_vma)
 		return -ENOMEM;

 	moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
 	if (moved_len < old_len) {
 		/*
 		 * Before moving the page tables from the new vma to
 		 * the old vma, we need to be sure the old vma is
 		 * queued after new vma in the same_anon_vma list to
 		 * prevent SMP races with rmap_walk (that could lead
 		 * rmap_walk to miss some page table).
 		 */
 		anon_vma_moveto_tail(vma);

 		/*
 		 * On error, move entries back from new area to old,
 		 * which will succeed since page tables still there,
 		 * and then proceed to unmap new area instead of old.
 		 */
 		move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
 		vma = new_vma;
 		old_len = new_len;
 		old_addr = new_addr;
 		new_addr = -ENOMEM;
 	}

 	/* Conceal VM_ACCOUNT so old reservation is not undone */
 	if (vm_flags & VM_ACCOUNT) {
 		vma->vm_flags &= ~VM_ACCOUNT;
 		excess = vma->vm_end - vma->vm_start - old_len;
 		if (old_addr > vma->vm_start &&
 		    old_addr + old_len < vma->vm_end)
 			split = 1;
 	}

 	/*
 	 * If we failed to move page tables we still do total_vm increment
 	 * since do_munmap() will decrement it by old_len == new_len.
 	 *
 	 * Since total_vm is about to be raised artificially high for a
 	 * moment, we need to restore high watermark afterwards: if stats
 	 * are taken meanwhile, total_vm and hiwater_vm appear too high.
 	 * If this were a serious issue, we'd add a flag to do_munmap().
 	 */
 	hiwater_vm = mm->hiwater_vm;
 	mm->total_vm += new_len >> PAGE_SHIFT;
 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);

 	if (do_munmap(mm, old_addr, old_len) < 0) {
 		/* OOM: unable to split vma, just get accounts right */
 		vm_unacct_memory(excess >> PAGE_SHIFT);
 		excess = 0;
 	}
 	mm->hiwater_vm = hiwater_vm;

 	/* Restore VM_ACCOUNT if one or two pieces of vma left */
 	if (excess) {
 		vma->vm_flags |= VM_ACCOUNT;
 		if (split)
 			vma->vm_next->vm_flags |= VM_ACCOUNT;
 	}

 	if (vm_flags & VM_LOCKED) {
 		mm->locked_vm += new_len >> PAGE_SHIFT;
 		if (new_len > old_len)
 			mlock_vma_pages_range(new_vma, new_addr + old_len,
 						       new_addr + new_len);
 	}

 	return new_addr;
 }

 static struct vm_area_struct *vma_to_resize(unsigned long addr,
 	unsigned long old_len, unsigned long new_len, unsigned long *p)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma = find_vma(mm, addr);

 	if (!vma || vma->vm_start > addr)
 		goto Efault;

 	if (is_vm_hugetlb_page(vma))
 		goto Einval;

 	/* We can't remap across vm area boundaries */
 	if (old_len > vma->vm_end - addr)
 		goto Efault;

 	/* Need to be careful about a growing mapping */
 	if (new_len > old_len) {
 		unsigned long pgoff;

 		if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
 			goto Efault;
 		pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
 		pgoff += vma->vm_pgoff;
 		if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
 			goto Einval;
 	}

 	if (vma->vm_flags & VM_LOCKED) {
 		unsigned long locked, lock_limit;
 		locked = mm->locked_vm << PAGE_SHIFT;
 		lock_limit = rlimit(RLIMIT_MEMLOCK);
 		locked += new_len - old_len;
 		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
 			goto Eagain;
 	}

 	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
 		goto Enomem;

 	if (vma->vm_flags & VM_ACCOUNT) {
 		unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
 		if (security_vm_enough_memory_mm(mm, charged))
 			goto Efault;
 		*p = charged;
 	}

 	return vma;

 Efault:	/* very odd choice for most of the cases, but... */
 	return ERR_PTR(-EFAULT);
 Einval:
 	return ERR_PTR(-EINVAL);
 Enomem:
 	return ERR_PTR(-ENOMEM);
 Eagain:
 	return ERR_PTR(-EAGAIN);
 }

 static unsigned long mremap_to(unsigned long addr,
 	unsigned long old_len, unsigned long new_addr,
 	unsigned long new_len)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long ret = -EINVAL;
 	unsigned long charged = 0;
 	unsigned long map_flags;

 	if (new_addr & ~PAGE_MASK)
 		goto out;

 	if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 		goto out;

 	/* Check if the location we're moving into overlaps the
 	 * old location at all, and fail if it does.
 	 */
 	if ((new_addr <= addr) && (new_addr+new_len) > addr)
 		goto out;

 	if ((addr <= new_addr) && (addr+old_len) > new_addr)
 		goto out;

 	ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 	if (ret)
 		goto out;

 	ret = do_munmap(mm, new_addr, new_len);
 	if (ret)
 		goto out;

 	if (old_len >= new_len) {
 		ret = do_munmap(mm, addr+new_len, old_len - new_len);
 		if (ret && old_len != new_len)
 			goto out;
 		old_len = new_len;
 	}

 	vma = vma_to_resize(addr, old_len, new_len, &charged);
 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		goto out;
 	}

 	map_flags = MAP_FIXED;
 	if (vma->vm_flags & VM_MAYSHARE)
 		map_flags |= MAP_SHARED;

 	ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
 				((addr - vma->vm_start) >> PAGE_SHIFT),
 				map_flags);
 	if (ret & ~PAGE_MASK)
 		goto out1;

 	ret = move_vma(vma, addr, old_len, new_len, new_addr);
 	if (!(ret & ~PAGE_MASK))
 		goto out;
 out1:
 	vm_unacct_memory(charged);

 out:
 	return ret;
 }

 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 {
 	unsigned long end = vma->vm_end + delta;
 	if (end < vma->vm_end) /* overflow */
 		return 0;
 	if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
 		return 0;
 	if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
 			      0, MAP_FIXED) & ~PAGE_MASK)
 		return 0;
 	return 1;
 }

 /*
  * Expand (or shrink) an existing mapping, potentially moving it at the
  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
  *
  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
  * This option implies MREMAP_MAYMOVE.
  */
 unsigned long do_mremap(unsigned long addr,
 	unsigned long old_len, unsigned long new_len,
 	unsigned long flags, unsigned long new_addr)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long ret = -EINVAL;
 	unsigned long charged = 0;

 	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
 		goto out;

 	if (addr & ~PAGE_MASK)
 		goto out;

 	old_len = PAGE_ALIGN(old_len);
 	new_len = PAGE_ALIGN(new_len);

 	/*
 	 * We allow a zero old-len as a special case
 	 * for DOS-emu "duplicate shm area" thing. But
 	 * a zero new-len is nonsensical.
 	 */
 	if (!new_len)
 		goto out;

 	if (flags & MREMAP_FIXED) {
 		if (flags & MREMAP_MAYMOVE)
 			ret = mremap_to(addr, old_len, new_addr, new_len);
 		goto out;
 	}

 	/*
 	 * Always allow a shrinking remap: that just unmaps
 	 * the unnecessary pages..
 	 * do_munmap does all the needed commit accounting
 	 */
 	if (old_len >= new_len) {
 		ret = do_munmap(mm, addr+new_len, old_len - new_len);
 		if (ret && old_len != new_len)
 			goto out;
 		ret = addr;
 		goto out;
 	}

 	/*
 	 * Ok, we need to grow..
 	 */
 	vma = vma_to_resize(addr, old_len, new_len, &charged);
 	if (IS_ERR(vma)) {
 		ret = PTR_ERR(vma);
 		goto out;
 	}

 	/* old_len exactly to the end of the area..
 	 */
 	if (old_len == vma->vm_end - addr) {
 		/* can we just expand the current mapping? */
 		if (vma_expandable(vma, new_len - old_len)) {
 			int pages = (new_len - old_len) >> PAGE_SHIFT;

 			if (vma_adjust(vma, vma->vm_start, addr + new_len,
 				       vma->vm_pgoff, NULL)) {
 				ret = -ENOMEM;
 				goto out;
 			}

 			mm->total_vm += pages;
 			vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 			if (vma->vm_flags & VM_LOCKED) {
 				mm->locked_vm += pages;
 				mlock_vma_pages_range(vma, addr + old_len,
 						   addr + new_len);
 			}
 			ret = addr;
 			goto out;
 		}
 	}

 	/*
 	 * We weren't able to just expand or shrink the area,
 	 * we need to create a new one and move it..
 	 */
 	ret = -ENOMEM;
 	if (flags & MREMAP_MAYMOVE) {
 		unsigned long map_flags = 0;
 		if (vma->vm_flags & VM_MAYSHARE)
 			map_flags |= MAP_SHARED;

 		new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
 					vma->vm_pgoff +
 					((addr - vma->vm_start) >> PAGE_SHIFT),
 					map_flags);
 		if (new_addr & ~PAGE_MASK) {
 			ret = new_addr;
 			goto out;
 		}

 		ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
 		if (ret)
 			goto out;
 		ret = move_vma(vma, addr, old_len, new_len, new_addr);
 	}
 out:
 	if (ret & ~PAGE_MASK)
 		vm_unacct_memory(charged);
 	return ret;
 }

 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 		unsigned long, new_len, unsigned long, flags,
 		unsigned long, new_addr)
 {
 	unsigned long ret;

 	down_write(&current->mm->mmap_sem);
 	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 	up_write(&current->mm->mmap_sem);
 	return ret;
 }
	/*
	* mm/mremap.c
	*
	* (C) Copyright 1996 Linus Torvalds
	*
	* Address space accounting code <alan@lxorguk.ukuu.org.uk>
	* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
	*/

	#include <linux/mm.h>
	#include <linux/hugetlb.h>
	#include <linux/shm.h>
	#include <linux/ksm.h>
	#include <linux/mman.h>
	#include <linux/swap.h>
	#include <linux/capability.h>
	#include <linux/fs.h>
	#include <linux/highmem.h>
	#include <linux/security.h>
	#include <linux/syscalls.h>
	#include <linux/mmu_notifier.h>

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

	#include "internal.h"

	static pmd_t get_old_pmd(struct mm_struct mm, unsigned long addr)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;

	pgd = pgd_offset(mm, addr);
	if (pgd_none_or_clear_bad(pgd))
	return NULL;

	pud = pud_offset(pgd, addr);
	if (pud_none_or_clear_bad(pud))
	return NULL;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd))
	return NULL;

	return pmd;
	}

	static pmd_t alloc_new_pmd(struct mm_struct mm, struct vm_area_struct *vma,
	unsigned long addr)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;

	pgd = pgd_offset(mm, addr);
	pud = pud_alloc(mm, pgd, addr);
	if (!pud)
	return NULL;

	pmd = pmd_alloc(mm, pud, addr);
	if (!pmd)
	return NULL;

	VM_BUG_ON(pmd_trans_huge(*pmd));

	return pmd;
	}

	static void move_ptes(struct vm_area_struct vma, pmd_t old_pmd,
	unsigned long old_addr, unsigned long old_end,
	struct vm_area_struct new_vma, pmd_t new_pmd,
	unsigned long new_addr)
	{
	struct address_space *mapping = NULL;
	struct mm_struct *mm = vma->vm_mm;
	pte_t old_pte, new_pte, pte;
	spinlock_t old_ptl, new_ptl;
	bool force_flush = false;
	unsigned long len = old_end - old_addr;

	if (vma->vm_file) {
	/*
	* Subtle point from Rajesh Venkatasubramanian: before
	* moving file-based ptes, we must lock truncate_pagecache
	* out, since it might clean the dst vma before the src vma,
	* and we propagate stale pages into the dst afterward.
	*/
	mapping = vma->vm_file->f_mapping;
	mutex_lock(&mapping->i_mmap_mutex);
	}

	/*
	* We don't have to worry about the ordering of src and dst
	* pte locks because exclusive mmap_sem prevents deadlock.
	*/
	old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
	new_pte = pte_offset_map(new_pmd, new_addr);
	new_ptl = pte_lockptr(mm, new_pmd);
	if (new_ptl != old_ptl)
	spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
	arch_enter_lazy_mmu_mode();

	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
	new_pte++, new_addr += PAGE_SIZE) {
	if (pte_none(*old_pte))
	continue;
	pte = ptep_get_and_clear(mm, old_addr, old_pte);
	/*
	* If we are remapping a valid PTE, make sure
	* to flush TLB before we drop the PTL for the PTE.
	*
	* NOTE! Both old and new PTL matter: the old one
	* for racing with page_mkclean(), the new one to
	* make sure the physical page stays valid until
	* the TLB entry for the old mapping has been
	* flushed.
	*/
	if (pte_present(pte))
	force_flush = true;
	pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
	set_pte_at(mm, new_addr, new_pte, pte);
	}

	arch_leave_lazy_mmu_mode();
	if (force_flush)
	flush_tlb_range(vma, old_end - len, old_end);
	if (new_ptl != old_ptl)
	spin_unlock(new_ptl);
	pte_unmap(new_pte - 1);
	pte_unmap_unlock(old_pte - 1, old_ptl);
	if (mapping)
	mutex_unlock(&mapping->i_mmap_mutex);
	}

	#define LATENCY_LIMIT (64 * PAGE_SIZE)

	unsigned long move_page_tables(struct vm_area_struct *vma,
	unsigned long old_addr, struct vm_area_struct *new_vma,
	unsigned long new_addr, unsigned long len)
	{
	unsigned long extent, next, old_end;
	pmd_t old_pmd, new_pmd;

	old_end = old_addr + len;
	flush_cache_range(vma, old_addr, old_end);

	mmu_notifier_invalidate_range_start(vma->vm_mm, old_addr, old_end);

	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
	cond_resched();
	next = (old_addr + PMD_SIZE) & PMD_MASK;
	/* even if next overflowed, extent below will be ok */
	extent = next - old_addr;
	if (extent > old_end - old_addr)
	extent = old_end - old_addr;
	old_pmd = get_old_pmd(vma->vm_mm, old_addr);
	if (!old_pmd)
	continue;
	new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
	if (!new_pmd)
	break;
	if (pmd_trans_huge(*old_pmd)) {
	int err = 0;
	if (extent == HPAGE_PMD_SIZE)
	err = move_huge_pmd(vma, new_vma, old_addr,
	new_addr, old_end,
	old_pmd, new_pmd);
	if (err > 0) {
	continue;
	} else if (!err) {
	split_huge_page_pmd(vma->vm_mm, old_pmd);
	}
	VM_BUG_ON(pmd_trans_huge(*old_pmd));
	}
	if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
	new_pmd, new_addr))
	break;
	next = (new_addr + PMD_SIZE) & PMD_MASK;
	if (extent > next - new_addr)
	extent = next - new_addr;
	if (extent > LATENCY_LIMIT)
	extent = LATENCY_LIMIT;
	move_ptes(vma, old_pmd, old_addr, old_addr + extent,
	new_vma, new_pmd, new_addr);
	}

	mmu_notifier_invalidate_range_end(vma->vm_mm, old_end-len, old_end);

	return len + old_addr - old_end; /* how much done */
	}

	static unsigned long move_vma(struct vm_area_struct *vma,
	unsigned long old_addr, unsigned long old_len,
	unsigned long new_len, unsigned long new_addr)
	{
	struct mm_struct *mm = vma->vm_mm;
	struct vm_area_struct *new_vma;
	unsigned long vm_flags = vma->vm_flags;
	unsigned long new_pgoff;
	unsigned long moved_len;
	unsigned long excess = 0;
	unsigned long hiwater_vm;
	int split = 0;
	int err;

	/*
	* We'd prefer to avoid failure later on in do_munmap:
	* which may split one vma into three before unmapping.
	*/
	if (mm->map_count >= sysctl_max_map_count - 3)
	return -ENOMEM;

	/*
	* Advise KSM to break any KSM pages in the area to be moved:
	* it would be confusing if they were to turn up at the new
	* location, where they happen to coincide with different KSM
	* pages recently unmapped. But leave vma->vm_flags as it was,
	* so KSM can come around to merge on vma and new_vma afterwards.
	*/
	err = ksm_madvise(vma, old_addr, old_addr + old_len,
	MADV_UNMERGEABLE, &vm_flags);
	if (err)
	return err;

	new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
	new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
	if (!new_vma)
	return -ENOMEM;

	moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
	if (moved_len < old_len) {
	/*
	* Before moving the page tables from the new vma to
	* the old vma, we need to be sure the old vma is
	* queued after new vma in the same_anon_vma list to
	* prevent SMP races with rmap_walk (that could lead
	* rmap_walk to miss some page table).
	*/
	anon_vma_moveto_tail(vma);

	/*
	* On error, move entries back from new area to old,
	* which will succeed since page tables still there,
	* and then proceed to unmap new area instead of old.
	*/
	move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
	vma = new_vma;
	old_len = new_len;
	old_addr = new_addr;
	new_addr = -ENOMEM;
	}

	/* Conceal VM_ACCOUNT so old reservation is not undone */
	if (vm_flags & VM_ACCOUNT) {
	vma->vm_flags &= ~VM_ACCOUNT;
	excess = vma->vm_end - vma->vm_start - old_len;
	if (old_addr > vma->vm_start &&
	old_addr + old_len < vma->vm_end)
	split = 1;
	}

	/*
	* If we failed to move page tables we still do total_vm increment
	* since do_munmap() will decrement it by old_len == new_len.
	*
	* Since total_vm is about to be raised artificially high for a
	* moment, we need to restore high watermark afterwards: if stats
	* are taken meanwhile, total_vm and hiwater_vm appear too high.
	* If this were a serious issue, we'd add a flag to do_munmap().
	*/
	hiwater_vm = mm->hiwater_vm;
	mm->total_vm += new_len >> PAGE_SHIFT;
	vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);

	if (do_munmap(mm, old_addr, old_len) < 0) {
	/* OOM: unable to split vma, just get accounts right */
	vm_unacct_memory(excess >> PAGE_SHIFT);
	excess = 0;
	}
	mm->hiwater_vm = hiwater_vm;

	/* Restore VM_ACCOUNT if one or two pieces of vma left */
	if (excess) {
	vma->vm_flags \|= VM_ACCOUNT;
	if (split)
	vma->vm_next->vm_flags \|= VM_ACCOUNT;
	}

	if (vm_flags & VM_LOCKED) {
	mm->locked_vm += new_len >> PAGE_SHIFT;
	if (new_len > old_len)
	mlock_vma_pages_range(new_vma, new_addr + old_len,
	new_addr + new_len);
	}

	return new_addr;
	}

	static struct vm_area_struct *vma_to_resize(unsigned long addr,
	unsigned long old_len, unsigned long new_len, unsigned long *p)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma = find_vma(mm, addr);

	if (!vma \|\| vma->vm_start > addr)
	goto Efault;

	if (is_vm_hugetlb_page(vma))
	goto Einval;

	/* We can't remap across vm area boundaries */
	if (old_len > vma->vm_end - addr)
	goto Efault;

	/* Need to be careful about a growing mapping */
	if (new_len > old_len) {
	unsigned long pgoff;

	if (vma->vm_flags & (VM_DONTEXPAND \| VM_PFNMAP))
	goto Efault;
	pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
	pgoff += vma->vm_pgoff;
	if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
	goto Einval;
	}

	if (vma->vm_flags & VM_LOCKED) {
	unsigned long locked, lock_limit;
	locked = mm->locked_vm << PAGE_SHIFT;
	lock_limit = rlimit(RLIMIT_MEMLOCK);
	locked += new_len - old_len;
	if (locked > lock_limit && !capable(CAP_IPC_LOCK))
	goto Eagain;
	}

	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
	goto Enomem;

	if (vma->vm_flags & VM_ACCOUNT) {
	unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
	if (security_vm_enough_memory_mm(mm, charged))
	goto Efault;
	*p = charged;
	}

	return vma;

	Efault: /* very odd choice for most of the cases, but... */
	return ERR_PTR(-EFAULT);
	Einval:
	return ERR_PTR(-EINVAL);
	Enomem:
	return ERR_PTR(-ENOMEM);
	Eagain:
	return ERR_PTR(-EAGAIN);
	}

	static unsigned long mremap_to(unsigned long addr,
	unsigned long old_len, unsigned long new_addr,
	unsigned long new_len)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long ret = -EINVAL;
	unsigned long charged = 0;
	unsigned long map_flags;

	if (new_addr & ~PAGE_MASK)
	goto out;

	if (new_len > TASK_SIZE \|\| new_addr > TASK_SIZE - new_len)
	goto out;

	/* Check if the location we're moving into overlaps the
	* old location at all, and fail if it does.
	*/
	if ((new_addr <= addr) && (new_addr+new_len) > addr)
	goto out;

	if ((addr <= new_addr) && (addr+old_len) > new_addr)
	goto out;

	ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
	if (ret)
	goto out;

	ret = do_munmap(mm, new_addr, new_len);
	if (ret)
	goto out;

	if (old_len >= new_len) {
	ret = do_munmap(mm, addr+new_len, old_len - new_len);
	if (ret && old_len != new_len)
	goto out;
	old_len = new_len;
	}

	vma = vma_to_resize(addr, old_len, new_len, &charged);
	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	goto out;
	}

	map_flags = MAP_FIXED;
	if (vma->vm_flags & VM_MAYSHARE)
	map_flags \|= MAP_SHARED;

	ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
	((addr - vma->vm_start) >> PAGE_SHIFT),
	map_flags);
	if (ret & ~PAGE_MASK)
	goto out1;

	ret = move_vma(vma, addr, old_len, new_len, new_addr);
	if (!(ret & ~PAGE_MASK))
	goto out;
	out1:
	vm_unacct_memory(charged);

	out:
	return ret;
	}

	static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
	{
	unsigned long end = vma->vm_end + delta;
	if (end < vma->vm_end) /* overflow */
	return 0;
	if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
	return 0;
	if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
	0, MAP_FIXED) & ~PAGE_MASK)
	return 0;
	return 1;
	}

	/*
	* Expand (or shrink) an existing mapping, potentially moving it at the
	* same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
	*
	* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
	* This option implies MREMAP_MAYMOVE.
	*/
	unsigned long do_mremap(unsigned long addr,
	unsigned long old_len, unsigned long new_len,
	unsigned long flags, unsigned long new_addr)
	{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long ret = -EINVAL;
	unsigned long charged = 0;

	if (flags & ~(MREMAP_FIXED \| MREMAP_MAYMOVE))
	goto out;

	if (addr & ~PAGE_MASK)
	goto out;

	old_len = PAGE_ALIGN(old_len);
	new_len = PAGE_ALIGN(new_len);

	/*
	* We allow a zero old-len as a special case
	* for DOS-emu "duplicate shm area" thing. But
	* a zero new-len is nonsensical.
	*/
	if (!new_len)
	goto out;

	if (flags & MREMAP_FIXED) {
	if (flags & MREMAP_MAYMOVE)
	ret = mremap_to(addr, old_len, new_addr, new_len);
	goto out;
	}

	/*
	* Always allow a shrinking remap: that just unmaps
	* the unnecessary pages..
	* do_munmap does all the needed commit accounting
	*/
	if (old_len >= new_len) {
	ret = do_munmap(mm, addr+new_len, old_len - new_len);
	if (ret && old_len != new_len)
	goto out;
	ret = addr;
	goto out;
	}

	/*
	* Ok, we need to grow..
	*/
	vma = vma_to_resize(addr, old_len, new_len, &charged);
	if (IS_ERR(vma)) {
	ret = PTR_ERR(vma);
	goto out;
	}

	/* old_len exactly to the end of the area..
	*/
	if (old_len == vma->vm_end - addr) {
	/* can we just expand the current mapping? */
	if (vma_expandable(vma, new_len - old_len)) {
	int pages = (new_len - old_len) >> PAGE_SHIFT;

	if (vma_adjust(vma, vma->vm_start, addr + new_len,
	vma->vm_pgoff, NULL)) {
	ret = -ENOMEM;
	goto out;
	}

	mm->total_vm += pages;
	vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
	if (vma->vm_flags & VM_LOCKED) {
	mm->locked_vm += pages;
	mlock_vma_pages_range(vma, addr + old_len,
	addr + new_len);
	}
	ret = addr;
	goto out;
	}
	}

	/*
	* We weren't able to just expand or shrink the area,
	* we need to create a new one and move it..
	*/
	ret = -ENOMEM;
	if (flags & MREMAP_MAYMOVE) {
	unsigned long map_flags = 0;
	if (vma->vm_flags & VM_MAYSHARE)
	map_flags \|= MAP_SHARED;

	new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
	vma->vm_pgoff +
	((addr - vma->vm_start) >> PAGE_SHIFT),
	map_flags);
	if (new_addr & ~PAGE_MASK) {
	ret = new_addr;
	goto out;
	}

	ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
	if (ret)
	goto out;
	ret = move_vma(vma, addr, old_len, new_len, new_addr);
	}
	out:
	if (ret & ~PAGE_MASK)
	vm_unacct_memory(charged);
	return ret;
	}

	SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
	unsigned long, new_len, unsigned long, flags,
	unsigned long, new_addr)
	{
	unsigned long ret;

	down_write(&current->mm->mmap_sem);
	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
	up_write(&current->mm->mmap_sem);
	return ret;
	}