[linux-2.6-block.git] / mm / mremap.c

/*
 *	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/slab.h>
#include <linux/shm.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_or_clear_bad(pmd))
		return NULL;

	return pmd;
}

static pmd_t *alloc_new_pmd(struct mm_struct *mm, 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;

	if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
		return NULL;

	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;
	unsigned long old_start;

	old_start = old_addr;
	mmu_notifier_invalidate_range_start(vma->vm_mm,
					    old_start, old_end);
	if (vma->vm_file) {
		/*
		 * Subtle point from Rajesh Venkatasubramanian: before
		 * moving file-based ptes, we must lock vmtruncate 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;
		spin_lock(&mapping->i_mmap_lock);
		if (new_vma->vm_truncate_count &&
		    new_vma->vm_truncate_count != vma->vm_truncate_count)
			new_vma->vm_truncate_count = 0;
	}

	/*
	 * 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_nested(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_clear_flush(vma, old_addr, old_pte);
		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 (new_ptl != old_ptl)
		spin_unlock(new_ptl);
	pte_unmap_nested(new_pte - 1);
	pte_unmap_unlock(old_pte - 1, old_ptl);
	if (mapping)
		spin_unlock(&mapping->i_mmap_lock);
	mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
}

#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);

	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
		cond_resched();
		next = (old_addr + PMD_SIZE) & PMD_MASK;
		if (next - 1 > old_end)
			next = old_end;
		extent = next - old_addr;
		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
		if (!old_pmd)
			continue;
		new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
		if (!new_pmd)
			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);
	}

	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;

	/*
	 * 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;

	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) {
		/*
		 * 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;
}

/*
 * 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;

	/* new_addr is only valid if MREMAP_FIXED is specified */
	if (flags & MREMAP_FIXED) {
		if (new_addr & ~PAGE_MASK)
			goto out;
		if (!(flags & MREMAP_MAYMOVE))
			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;
	}

	/*
	 * 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;
		if (!(flags & MREMAP_FIXED) || (new_addr == addr))
			goto out;
		old_len = new_len;
	}

	/*
	 * Ok, we need to grow..  or relocate.
	 */
	ret = -EFAULT;
	vma = find_vma(mm, addr);
	if (!vma || vma->vm_start > addr)
		goto out;
	if (is_vm_hugetlb_page(vma)) {
		ret = -EINVAL;
		goto out;
	}
	/* We can't remap across vm area boundaries */
	if (old_len > vma->vm_end - addr)
		goto out;
	if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
		if (new_len > old_len)
			goto out;
	}
	if (vma->vm_flags & VM_LOCKED) {
		unsigned long locked, lock_limit;
		locked = mm->locked_vm << PAGE_SHIFT;
		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
		locked += new_len - old_len;
		ret = -EAGAIN;
		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
			goto out;
	}
	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
		ret = -ENOMEM;
		goto out;
	}

	if (vma->vm_flags & VM_ACCOUNT) {
		charged = (new_len - old_len) >> PAGE_SHIFT;
		if (security_vm_enough_memory(charged))
			goto out_nc;
	}

	/* old_len exactly to the end of the area..
	 * And we're not relocating the area.
	 */
	if (old_len == vma->vm_end - addr &&
	    !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
	    (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
		unsigned long max_addr = TASK_SIZE;
		if (vma->vm_next)
			max_addr = vma->vm_next->vm_start;
		/* can we just expand the current mapping? */
		if (max_addr - addr >= new_len) {
			int pages = (new_len - old_len) >> PAGE_SHIFT;

			vma_adjust(vma, vma->vm_start,
				addr + new_len, vma->vm_pgoff, NULL);

			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) {
		if (!(flags & MREMAP_FIXED)) {
			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, 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);
out_nc:
	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;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* mm/mremap.c
	3	*
	4	* (C) Copyright 1996 Linus Torvalds
	5	*
046c6884	6	* Address space accounting code <alan@lxorguk.ukuu.org.uk>
1da177e4 LT	7	* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
	8	*/
	9
	10	#include <linux/mm.h>
	11	#include <linux/hugetlb.h>
	12	#include <linux/slab.h>
	13	#include <linux/shm.h>
	14	#include <linux/mman.h>
	15	#include <linux/swap.h>
c59ede7b	16	#include <linux/capability.h>
1da177e4 LT	17	#include <linux/fs.h>
	18	#include <linux/highmem.h>
	19	#include <linux/security.h>
	20	#include <linux/syscalls.h>
cddb8a5c	21	#include <linux/mmu_notifier.h>
1da177e4 LT	22
	23	#include <asm/uaccess.h>
	24	#include <asm/cacheflush.h>
	25	#include <asm/tlbflush.h>
	26
ba470de4 RR	27	#include "internal.h"
ba470de4 RR	28
7be7a546	29	static pmd_t get_old_pmd(struct mm_struct mm, unsigned long addr)
1da177e4 LT	30	{
	31	pgd_t *pgd;
	32	pud_t *pud;
	33	pmd_t *pmd;
	34
	35	pgd = pgd_offset(mm, addr);
	36	if (pgd_none_or_clear_bad(pgd))
	37	return NULL;
	38
	39	pud = pud_offset(pgd, addr);
	40	if (pud_none_or_clear_bad(pud))
	41	return NULL;
	42
	43	pmd = pmd_offset(pud, addr);
	44	if (pmd_none_or_clear_bad(pmd))
	45	return NULL;
	46
7be7a546	47	return pmd;
1da177e4 LT	48	}
1da177e4 LT	49
7be7a546	50	static pmd_t alloc_new_pmd(struct mm_struct mm, unsigned long addr)
1da177e4 LT	51	{
	52	pgd_t *pgd;
	53	pud_t *pud;
c74df32c	54	pmd_t *pmd;
1da177e4 LT	55
1da177e4 LT	56	pgd = pgd_offset(mm, addr);
1da177e4 LT	57	pud = pud_alloc(mm, pgd, addr);
1da177e4 LT	58	if (!pud)
c74df32c	59	return NULL;
7be7a546	60
1da177e4	61	pmd = pmd_alloc(mm, pud, addr);
7be7a546	62	if (!pmd)
c74df32c	63	return NULL;
7be7a546	64
1bb3630e	65	if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
c74df32c HD	66	return NULL;
c74df32c HD	67
7be7a546	68	return pmd;
1da177e4 LT	69	}
1da177e4 LT	70
7be7a546 HD	71	static void move_ptes(struct vm_area_struct vma, pmd_t old_pmd,
	72	unsigned long old_addr, unsigned long old_end,
	73	struct vm_area_struct new_vma, pmd_t new_pmd,
	74	unsigned long new_addr)
1da177e4 LT	75	{
	76	struct address_space *mapping = NULL;
	77	struct mm_struct *mm = vma->vm_mm;
7be7a546	78	pte_t old_pte, new_pte, pte;
4c21e2f2	79	spinlock_t old_ptl, new_ptl;
cddb8a5c	80	unsigned long old_start;
1da177e4	81
cddb8a5c AA	82	old_start = old_addr;
	83	mmu_notifier_invalidate_range_start(vma->vm_mm,
	84	old_start, old_end);
1da177e4 LT	85	if (vma->vm_file) {
	86	/*
	87	* Subtle point from Rajesh Venkatasubramanian: before
	88	* moving file-based ptes, we must lock vmtruncate out,
	89	* since it might clean the dst vma before the src vma,
	90	* and we propagate stale pages into the dst afterward.
	91	*/
	92	mapping = vma->vm_file->f_mapping;
	93	spin_lock(&mapping->i_mmap_lock);
	94	if (new_vma->vm_truncate_count &&
	95	new_vma->vm_truncate_count != vma->vm_truncate_count)
	96	new_vma->vm_truncate_count = 0;
	97	}
1da177e4	98
4c21e2f2 HD	99	/*
	100	* We don't have to worry about the ordering of src and dst
	101	* pte locks because exclusive mmap_sem prevents deadlock.
	102	*/
c74df32c HD	103	old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
c74df32c HD	104	new_pte = pte_offset_map_nested(new_pmd, new_addr);
4c21e2f2 HD	105	new_ptl = pte_lockptr(mm, new_pmd);
4c21e2f2 HD	106	if (new_ptl != old_ptl)
f20dc5f7	107	spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
6606c3e0	108	arch_enter_lazy_mmu_mode();
7be7a546 HD	109
	110	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
	111	new_pte++, new_addr += PAGE_SIZE) {
	112	if (pte_none(*old_pte))
	113	continue;
	114	pte = ptep_clear_flush(vma, old_addr, old_pte);
7be7a546 HD	115	pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
7be7a546 HD	116	set_pte_at(mm, new_addr, new_pte, pte);
1da177e4	117	}
7be7a546	118
6606c3e0	119	arch_leave_lazy_mmu_mode();
4c21e2f2 HD	120	if (new_ptl != old_ptl)
4c21e2f2 HD	121	spin_unlock(new_ptl);
7be7a546	122	pte_unmap_nested(new_pte - 1);
c74df32c	123	pte_unmap_unlock(old_pte - 1, old_ptl);
1da177e4 LT	124	if (mapping)
1da177e4 LT	125	spin_unlock(&mapping->i_mmap_lock);
cddb8a5c	126	mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
1da177e4 LT	127	}
1da177e4 LT	128
7be7a546 HD	129	#define LATENCY_LIMIT (64 * PAGE_SIZE)
7be7a546 HD	130
b6a2fea3	131	unsigned long move_page_tables(struct vm_area_struct *vma,
1da177e4 LT	132	unsigned long old_addr, struct vm_area_struct *new_vma,
	133	unsigned long new_addr, unsigned long len)
	134	{
7be7a546 HD	135	unsigned long extent, next, old_end;
7be7a546 HD	136	pmd_t old_pmd, new_pmd;
1da177e4	137
7be7a546 HD	138	old_end = old_addr + len;
7be7a546 HD	139	flush_cache_range(vma, old_addr, old_end);
1da177e4	140
7be7a546	141	for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
1da177e4	142	cond_resched();
7be7a546 HD	143	next = (old_addr + PMD_SIZE) & PMD_MASK;
	144	if (next - 1 > old_end)
	145	next = old_end;
	146	extent = next - old_addr;
	147	old_pmd = get_old_pmd(vma->vm_mm, old_addr);
	148	if (!old_pmd)
	149	continue;
	150	new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
	151	if (!new_pmd)
	152	break;
	153	next = (new_addr + PMD_SIZE) & PMD_MASK;
	154	if (extent > next - new_addr)
	155	extent = next - new_addr;
	156	if (extent > LATENCY_LIMIT)
	157	extent = LATENCY_LIMIT;
	158	move_ptes(vma, old_pmd, old_addr, old_addr + extent,
	159	new_vma, new_pmd, new_addr);
1da177e4	160	}
7be7a546 HD	161
7be7a546 HD	162	return len + old_addr - old_end; /* how much done */
1da177e4 LT	163	}
	164
	165	static unsigned long move_vma(struct vm_area_struct *vma,
	166	unsigned long old_addr, unsigned long old_len,
	167	unsigned long new_len, unsigned long new_addr)
	168	{
	169	struct mm_struct *mm = vma->vm_mm;
	170	struct vm_area_struct *new_vma;
	171	unsigned long vm_flags = vma->vm_flags;
	172	unsigned long new_pgoff;
	173	unsigned long moved_len;
	174	unsigned long excess = 0;
365e9c87	175	unsigned long hiwater_vm;
1da177e4 LT	176	int split = 0;
	177
	178	/*
	179	* We'd prefer to avoid failure later on in do_munmap:
	180	* which may split one vma into three before unmapping.
	181	*/
	182	if (mm->map_count >= sysctl_max_map_count - 3)
	183	return -ENOMEM;
	184
	185	new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
	186	new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
	187	if (!new_vma)
	188	return -ENOMEM;
	189
	190	moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
	191	if (moved_len < old_len) {
	192	/*
	193	* On error, move entries back from new area to old,
	194	* which will succeed since page tables still there,
	195	* and then proceed to unmap new area instead of old.
	196	*/
	197	move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
	198	vma = new_vma;
	199	old_len = new_len;
	200	old_addr = new_addr;
	201	new_addr = -ENOMEM;
	202	}
	203
	204	/* Conceal VM_ACCOUNT so old reservation is not undone */
	205	if (vm_flags & VM_ACCOUNT) {
	206	vma->vm_flags &= ~VM_ACCOUNT;
	207	excess = vma->vm_end - vma->vm_start - old_len;
	208	if (old_addr > vma->vm_start &&
	209	old_addr + old_len < vma->vm_end)
	210	split = 1;
	211	}
	212
71799062	213	/*
365e9c87 HD	214	* If we failed to move page tables we still do total_vm increment
	215	* since do_munmap() will decrement it by old_len == new_len.
	216	*
	217	* Since total_vm is about to be raised artificially high for a
	218	* moment, we need to restore high watermark afterwards: if stats
	219	* are taken meanwhile, total_vm and hiwater_vm appear too high.
	220	* If this were a serious issue, we'd add a flag to do_munmap().
71799062	221	*/
365e9c87	222	hiwater_vm = mm->hiwater_vm;
71799062	223	mm->total_vm += new_len >> PAGE_SHIFT;
ab50b8ed	224	vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
71799062	225
1da177e4 LT	226	if (do_munmap(mm, old_addr, old_len) < 0) {
	227	/* OOM: unable to split vma, just get accounts right */
	228	vm_unacct_memory(excess >> PAGE_SHIFT);
	229	excess = 0;
	230	}
365e9c87	231	mm->hiwater_vm = hiwater_vm;
1da177e4 LT	232
	233	/* Restore VM_ACCOUNT if one or two pieces of vma left */
	234	if (excess) {
	235	vma->vm_flags \|= VM_ACCOUNT;
	236	if (split)
	237	vma->vm_next->vm_flags \|= VM_ACCOUNT;
	238	}
	239
1da177e4 LT	240	if (vm_flags & VM_LOCKED) {
	241	mm->locked_vm += new_len >> PAGE_SHIFT;
	242	if (new_len > old_len)
ba470de4 RR	243	mlock_vma_pages_range(new_vma, new_addr + old_len,
ba470de4 RR	244	new_addr + new_len);
1da177e4 LT	245	}
	246
	247	return new_addr;
	248	}
	249
	250	/*
	251	* Expand (or shrink) an existing mapping, potentially moving it at the
	252	* same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
	253	*
	254	* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
	255	* This option implies MREMAP_MAYMOVE.
	256	*/
	257	unsigned long do_mremap(unsigned long addr,
	258	unsigned long old_len, unsigned long new_len,
	259	unsigned long flags, unsigned long new_addr)
	260	{
d0de32d9	261	struct mm_struct *mm = current->mm;
1da177e4 LT	262	struct vm_area_struct *vma;
	263	unsigned long ret = -EINVAL;
	264	unsigned long charged = 0;
	265
	266	if (flags & ~(MREMAP_FIXED \| MREMAP_MAYMOVE))
	267	goto out;
	268
	269	if (addr & ~PAGE_MASK)
	270	goto out;
	271
	272	old_len = PAGE_ALIGN(old_len);
	273	new_len = PAGE_ALIGN(new_len);
	274
	275	/*
	276	* We allow a zero old-len as a special case
	277	* for DOS-emu "duplicate shm area" thing. But
	278	* a zero new-len is nonsensical.
	279	*/
	280	if (!new_len)
	281	goto out;
	282
	283	/* new_addr is only valid if MREMAP_FIXED is specified */
	284	if (flags & MREMAP_FIXED) {
	285	if (new_addr & ~PAGE_MASK)
	286	goto out;
	287	if (!(flags & MREMAP_MAYMOVE))
	288	goto out;
	289
	290	if (new_len > TASK_SIZE \|\| new_addr > TASK_SIZE - new_len)
	291	goto out;
	292
	293	/* Check if the location we're moving into overlaps the
	294	* old location at all, and fail if it does.
	295	*/
	296	if ((new_addr <= addr) && (new_addr+new_len) > addr)
	297	goto out;
	298
	299	if ((addr <= new_addr) && (addr+old_len) > new_addr)
	300	goto out;
	301
c80544dc	302	ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
ed032189 EP	303	if (ret)
	304	goto out;
	305
d0de32d9	306	ret = do_munmap(mm, new_addr, new_len);
1da177e4 LT	307	if (ret)
	308	goto out;
	309	}
	310
	311	/*
	312	* Always allow a shrinking remap: that just unmaps
	313	* the unnecessary pages..
	314	* do_munmap does all the needed commit accounting
	315	*/
	316	if (old_len >= new_len) {
d0de32d9	317	ret = do_munmap(mm, addr+new_len, old_len - new_len);
1da177e4 LT	318	if (ret && old_len != new_len)
	319	goto out;
	320	ret = addr;
	321	if (!(flags & MREMAP_FIXED) \|\| (new_addr == addr))
	322	goto out;
	323	old_len = new_len;
	324	}
	325
	326	/*
	327	* Ok, we need to grow.. or relocate.
	328	*/
	329	ret = -EFAULT;
d0de32d9	330	vma = find_vma(mm, addr);
1da177e4 LT	331	if (!vma \|\| vma->vm_start > addr)
	332	goto out;
	333	if (is_vm_hugetlb_page(vma)) {
	334	ret = -EINVAL;
	335	goto out;
	336	}
	337	/* We can't remap across vm area boundaries */
	338	if (old_len > vma->vm_end - addr)
	339	goto out;
4d7672b4	340	if (vma->vm_flags & (VM_DONTEXPAND \| VM_PFNMAP)) {
1da177e4 LT	341	if (new_len > old_len)
	342	goto out;
	343	}
	344	if (vma->vm_flags & VM_LOCKED) {
	345	unsigned long locked, lock_limit;
d0de32d9	346	locked = mm->locked_vm << PAGE_SHIFT;
1da177e4 LT	347	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
	348	locked += new_len - old_len;
	349	ret = -EAGAIN;
	350	if (locked > lock_limit && !capable(CAP_IPC_LOCK))
	351	goto out;
	352	}
d0de32d9	353	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
119f657c	354	ret = -ENOMEM;
1da177e4	355	goto out;
119f657c	356	}
1da177e4 LT	357
	358	if (vma->vm_flags & VM_ACCOUNT) {
	359	charged = (new_len - old_len) >> PAGE_SHIFT;
	360	if (security_vm_enough_memory(charged))
	361	goto out_nc;
	362	}
	363
	364	/* old_len exactly to the end of the area..
	365	* And we're not relocating the area.
	366	*/
	367	if (old_len == vma->vm_end - addr &&
	368	!((flags & MREMAP_FIXED) && (addr != new_addr)) &&
	369	(old_len != new_len \|\| !(flags & MREMAP_MAYMOVE))) {
	370	unsigned long max_addr = TASK_SIZE;
	371	if (vma->vm_next)
	372	max_addr = vma->vm_next->vm_start;
	373	/* can we just expand the current mapping? */
	374	if (max_addr - addr >= new_len) {
	375	int pages = (new_len - old_len) >> PAGE_SHIFT;
	376
	377	vma_adjust(vma, vma->vm_start,
	378	addr + new_len, vma->vm_pgoff, NULL);
	379
d0de32d9 HD	380	mm->total_vm += pages;
d0de32d9 HD	381	vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
1da177e4	382	if (vma->vm_flags & VM_LOCKED) {
d0de32d9	383	mm->locked_vm += pages;
ba470de4	384	mlock_vma_pages_range(vma, addr + old_len,
1da177e4 LT	385	addr + new_len);
	386	}
	387	ret = addr;
	388	goto out;
	389	}
	390	}
	391
	392	/*
	393	* We weren't able to just expand or shrink the area,
	394	* we need to create a new one and move it..
	395	*/
	396	ret = -ENOMEM;
	397	if (flags & MREMAP_MAYMOVE) {
	398	if (!(flags & MREMAP_FIXED)) {
	399	unsigned long map_flags = 0;
	400	if (vma->vm_flags & VM_MAYSHARE)
	401	map_flags \|= MAP_SHARED;
	402
	403	new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
	404	vma->vm_pgoff, map_flags);
ed032189 EP	405	if (new_addr & ~PAGE_MASK) {
	406	ret = new_addr;
	407	goto out;
	408	}
	409
c80544dc	410	ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
ed032189	411	if (ret)
1da177e4 LT	412	goto out;
	413	}
	414	ret = move_vma(vma, addr, old_len, new_len, new_addr);
	415	}
	416	out:
	417	if (ret & ~PAGE_MASK)
	418	vm_unacct_memory(charged);
	419	out_nc:
	420	return ret;
	421	}
	422
6a6160a7 HC	423	SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
	424	unsigned long, new_len, unsigned long, flags,
	425	unsigned long, new_addr)
1da177e4 LT	426	{
	427	unsigned long ret;
	428
	429	down_write(&current->mm->mmap_sem);
	430	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
	431	up_write(&current->mm->mmap_sem);
	432	return ret;
	433	}