436 lines
11 KiB
C
436 lines
11 KiB
C
/*
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* mm/mremap.c
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*
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* (C) Copyright 1996 Linus Torvalds
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*
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* Address space accounting code <alan@redhat.com>
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* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
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*/
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#include <linux/mm.h>
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#include <linux/hugetlb.h>
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#include <linux/slab.h>
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#include <linux/shm.h>
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#include <linux/mman.h>
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#include <linux/swap.h>
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#include <linux/fs.h>
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#include <linux/highmem.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <asm/uaccess.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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static pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte = NULL;
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pgd = pgd_offset(mm, addr);
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if (pgd_none_or_clear_bad(pgd))
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goto end;
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pud = pud_offset(pgd, addr);
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if (pud_none_or_clear_bad(pud))
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goto end;
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pmd = pmd_offset(pud, addr);
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if (pmd_none_or_clear_bad(pmd))
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goto end;
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pte = pte_offset_map_nested(pmd, addr);
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if (pte_none(*pte)) {
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pte_unmap_nested(pte);
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pte = NULL;
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}
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end:
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return pte;
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}
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static pte_t *get_one_pte_map(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pgd = pgd_offset(mm, addr);
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if (pgd_none_or_clear_bad(pgd))
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return NULL;
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pud = pud_offset(pgd, addr);
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if (pud_none_or_clear_bad(pud))
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return NULL;
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pmd = pmd_offset(pud, addr);
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if (pmd_none_or_clear_bad(pmd))
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return NULL;
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return pte_offset_map(pmd, addr);
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}
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static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte = NULL;
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pgd = pgd_offset(mm, addr);
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pud = pud_alloc(mm, pgd, addr);
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if (!pud)
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return NULL;
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pmd = pmd_alloc(mm, pud, addr);
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if (pmd)
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pte = pte_alloc_map(mm, pmd, addr);
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return pte;
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}
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static int
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move_one_page(struct vm_area_struct *vma, unsigned long old_addr,
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struct vm_area_struct *new_vma, unsigned long new_addr)
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{
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struct address_space *mapping = NULL;
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struct mm_struct *mm = vma->vm_mm;
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int error = 0;
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pte_t *src, *dst;
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if (vma->vm_file) {
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/*
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* Subtle point from Rajesh Venkatasubramanian: before
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* moving file-based ptes, we must lock vmtruncate out,
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* since it might clean the dst vma before the src vma,
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* and we propagate stale pages into the dst afterward.
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*/
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mapping = vma->vm_file->f_mapping;
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spin_lock(&mapping->i_mmap_lock);
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if (new_vma->vm_truncate_count &&
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new_vma->vm_truncate_count != vma->vm_truncate_count)
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new_vma->vm_truncate_count = 0;
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}
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spin_lock(&mm->page_table_lock);
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src = get_one_pte_map_nested(mm, old_addr);
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if (src) {
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/*
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* Look to see whether alloc_one_pte_map needs to perform a
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* memory allocation. If it does then we need to drop the
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* atomic kmap
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*/
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dst = get_one_pte_map(mm, new_addr);
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if (unlikely(!dst)) {
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pte_unmap_nested(src);
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if (mapping)
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spin_unlock(&mapping->i_mmap_lock);
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dst = alloc_one_pte_map(mm, new_addr);
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if (mapping && !spin_trylock(&mapping->i_mmap_lock)) {
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spin_unlock(&mm->page_table_lock);
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spin_lock(&mapping->i_mmap_lock);
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spin_lock(&mm->page_table_lock);
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}
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src = get_one_pte_map_nested(mm, old_addr);
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}
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/*
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* Since alloc_one_pte_map can drop and re-acquire
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* page_table_lock, we should re-check the src entry...
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*/
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if (src) {
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if (dst) {
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pte_t pte;
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pte = ptep_clear_flush(vma, old_addr, src);
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/* ZERO_PAGE can be dependant on virtual addr */
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if (pfn_valid(pte_pfn(pte)) &&
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pte_page(pte) == ZERO_PAGE(old_addr))
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pte = pte_wrprotect(mk_pte(ZERO_PAGE(new_addr), new_vma->vm_page_prot));
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set_pte_at(mm, new_addr, dst, pte);
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} else
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error = -ENOMEM;
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pte_unmap_nested(src);
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}
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if (dst)
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pte_unmap(dst);
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}
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spin_unlock(&mm->page_table_lock);
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if (mapping)
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spin_unlock(&mapping->i_mmap_lock);
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return error;
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}
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static unsigned long move_page_tables(struct vm_area_struct *vma,
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unsigned long old_addr, struct vm_area_struct *new_vma,
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unsigned long new_addr, unsigned long len)
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{
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unsigned long offset;
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flush_cache_range(vma, old_addr, old_addr + len);
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/*
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* This is not the clever way to do this, but we're taking the
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* easy way out on the assumption that most remappings will be
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* only a few pages.. This also makes error recovery easier.
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*/
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for (offset = 0; offset < len; offset += PAGE_SIZE) {
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if (move_one_page(vma, old_addr + offset,
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new_vma, new_addr + offset) < 0)
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break;
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cond_resched();
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}
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return offset;
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}
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static unsigned long move_vma(struct vm_area_struct *vma,
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unsigned long old_addr, unsigned long old_len,
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unsigned long new_len, unsigned long new_addr)
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{
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struct mm_struct *mm = vma->vm_mm;
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struct vm_area_struct *new_vma;
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unsigned long vm_flags = vma->vm_flags;
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unsigned long new_pgoff;
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unsigned long moved_len;
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unsigned long excess = 0;
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int split = 0;
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/*
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* We'd prefer to avoid failure later on in do_munmap:
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* which may split one vma into three before unmapping.
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*/
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if (mm->map_count >= sysctl_max_map_count - 3)
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return -ENOMEM;
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new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
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new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
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if (!new_vma)
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return -ENOMEM;
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moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
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if (moved_len < old_len) {
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/*
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* On error, move entries back from new area to old,
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* which will succeed since page tables still there,
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* and then proceed to unmap new area instead of old.
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*/
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move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
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vma = new_vma;
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old_len = new_len;
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old_addr = new_addr;
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new_addr = -ENOMEM;
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}
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/* Conceal VM_ACCOUNT so old reservation is not undone */
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if (vm_flags & VM_ACCOUNT) {
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vma->vm_flags &= ~VM_ACCOUNT;
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excess = vma->vm_end - vma->vm_start - old_len;
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if (old_addr > vma->vm_start &&
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old_addr + old_len < vma->vm_end)
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split = 1;
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}
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/*
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* if we failed to move page tables we still do total_vm increment
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* since do_munmap() will decrement it by old_len == new_len
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*/
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mm->total_vm += new_len >> PAGE_SHIFT;
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__vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
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if (do_munmap(mm, old_addr, old_len) < 0) {
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/* OOM: unable to split vma, just get accounts right */
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vm_unacct_memory(excess >> PAGE_SHIFT);
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excess = 0;
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}
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/* Restore VM_ACCOUNT if one or two pieces of vma left */
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if (excess) {
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vma->vm_flags |= VM_ACCOUNT;
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if (split)
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vma->vm_next->vm_flags |= VM_ACCOUNT;
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}
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if (vm_flags & VM_LOCKED) {
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mm->locked_vm += new_len >> PAGE_SHIFT;
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if (new_len > old_len)
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make_pages_present(new_addr + old_len,
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new_addr + new_len);
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}
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return new_addr;
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}
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/*
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* Expand (or shrink) an existing mapping, potentially moving it at the
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* same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
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*
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* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
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* This option implies MREMAP_MAYMOVE.
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*/
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unsigned long do_mremap(unsigned long addr,
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unsigned long old_len, unsigned long new_len,
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unsigned long flags, unsigned long new_addr)
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{
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struct vm_area_struct *vma;
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unsigned long ret = -EINVAL;
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unsigned long charged = 0;
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if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
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goto out;
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if (addr & ~PAGE_MASK)
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goto out;
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old_len = PAGE_ALIGN(old_len);
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new_len = PAGE_ALIGN(new_len);
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/*
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* We allow a zero old-len as a special case
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* for DOS-emu "duplicate shm area" thing. But
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* a zero new-len is nonsensical.
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*/
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if (!new_len)
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goto out;
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/* new_addr is only valid if MREMAP_FIXED is specified */
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if (flags & MREMAP_FIXED) {
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if (new_addr & ~PAGE_MASK)
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goto out;
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if (!(flags & MREMAP_MAYMOVE))
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goto out;
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if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
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goto out;
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/* Check if the location we're moving into overlaps the
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* old location at all, and fail if it does.
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*/
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if ((new_addr <= addr) && (new_addr+new_len) > addr)
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goto out;
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if ((addr <= new_addr) && (addr+old_len) > new_addr)
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goto out;
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ret = do_munmap(current->mm, new_addr, new_len);
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if (ret)
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goto out;
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}
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/*
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* Always allow a shrinking remap: that just unmaps
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* the unnecessary pages..
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* do_munmap does all the needed commit accounting
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*/
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if (old_len >= new_len) {
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ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
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if (ret && old_len != new_len)
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goto out;
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ret = addr;
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if (!(flags & MREMAP_FIXED) || (new_addr == addr))
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goto out;
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old_len = new_len;
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}
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/*
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* Ok, we need to grow.. or relocate.
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*/
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ret = -EFAULT;
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vma = find_vma(current->mm, addr);
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if (!vma || vma->vm_start > addr)
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goto out;
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if (is_vm_hugetlb_page(vma)) {
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ret = -EINVAL;
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goto out;
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}
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/* We can't remap across vm area boundaries */
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if (old_len > vma->vm_end - addr)
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goto out;
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if (vma->vm_flags & VM_DONTEXPAND) {
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if (new_len > old_len)
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goto out;
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}
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if (vma->vm_flags & VM_LOCKED) {
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unsigned long locked, lock_limit;
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locked = current->mm->locked_vm << PAGE_SHIFT;
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lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
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locked += new_len - old_len;
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ret = -EAGAIN;
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if (locked > lock_limit && !capable(CAP_IPC_LOCK))
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goto out;
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}
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if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) {
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ret = -ENOMEM;
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goto out;
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}
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if (vma->vm_flags & VM_ACCOUNT) {
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charged = (new_len - old_len) >> PAGE_SHIFT;
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if (security_vm_enough_memory(charged))
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goto out_nc;
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}
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/* old_len exactly to the end of the area..
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* And we're not relocating the area.
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*/
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if (old_len == vma->vm_end - addr &&
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!((flags & MREMAP_FIXED) && (addr != new_addr)) &&
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(old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
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unsigned long max_addr = TASK_SIZE;
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if (vma->vm_next)
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max_addr = vma->vm_next->vm_start;
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/* can we just expand the current mapping? */
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if (max_addr - addr >= new_len) {
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int pages = (new_len - old_len) >> PAGE_SHIFT;
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vma_adjust(vma, vma->vm_start,
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addr + new_len, vma->vm_pgoff, NULL);
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current->mm->total_vm += pages;
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__vm_stat_account(vma->vm_mm, vma->vm_flags,
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vma->vm_file, pages);
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if (vma->vm_flags & VM_LOCKED) {
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current->mm->locked_vm += pages;
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make_pages_present(addr + old_len,
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addr + new_len);
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}
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ret = addr;
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goto out;
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}
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}
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/*
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* We weren't able to just expand or shrink the area,
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* we need to create a new one and move it..
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*/
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ret = -ENOMEM;
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if (flags & MREMAP_MAYMOVE) {
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if (!(flags & MREMAP_FIXED)) {
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unsigned long map_flags = 0;
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if (vma->vm_flags & VM_MAYSHARE)
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map_flags |= MAP_SHARED;
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new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
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vma->vm_pgoff, map_flags);
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ret = new_addr;
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if (new_addr & ~PAGE_MASK)
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goto out;
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}
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ret = move_vma(vma, addr, old_len, new_len, new_addr);
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}
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out:
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if (ret & ~PAGE_MASK)
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vm_unacct_memory(charged);
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out_nc:
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return ret;
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}
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asmlinkage unsigned long sys_mremap(unsigned long addr,
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unsigned long old_len, unsigned long new_len,
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unsigned long flags, unsigned long new_addr)
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{
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unsigned long ret;
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down_write(¤t->mm->mmap_sem);
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ret = do_mremap(addr, old_len, new_len, flags, new_addr);
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up_write(¤t->mm->mmap_sem);
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return ret;
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}
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