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    Subject[PATCH 08/21] mm: ia64 use expand_upwards
    ia64 has expand_backing_store function for growing its Register Backing
    Store vma upwards. But more complete code for this purpose is found in
    the CONFIG_STACK_GROWSUP part of mm/mmap.c. Uglify its #ifdefs further
    to provide expand_upwards for ia64 as well as expand_stack for parisc.

    The Register Backing Store vma should be marked VM_ACCOUNT. Implement
    the intention of growing it only a page at a time, instead of passing an
    address outside of the vma to handle_mm_fault, with unknown consequences.

    Signed-off-by: Hugh Dickins <hugh@veritas.com>
    ---

    arch/ia64/mm/fault.c | 34 +++++++---------------------------
    arch/ia64/mm/init.c | 2 +-
    include/linux/mm.h | 3 ++-
    mm/mmap.c | 17 ++++++++++++++---
    4 files changed, 24 insertions(+), 32 deletions(-)

    --- mm07/arch/ia64/mm/fault.c 2005-09-30 11:58:53.000000000 +0100
    +++ mm08/arch/ia64/mm/fault.c 2005-10-11 23:55:38.000000000 +0100
    @@ -20,32 +20,6 @@
    extern void die (char *, struct pt_regs *, long);

    /*
    - * This routine is analogous to expand_stack() but instead grows the
    - * register backing store (which grows towards higher addresses).
    - * Since the register backing store is access sequentially, we
    - * disallow growing the RBS by more than a page at a time. Note that
    - * the VM_GROWSUP flag can be set on any VM area but that's fine
    - * because the total process size is still limited by RLIMIT_STACK and
    - * RLIMIT_AS.
    - */
    -static inline long
    -expand_backing_store (struct vm_area_struct *vma, unsigned long address)
    -{
    - unsigned long grow;
    -
    - grow = PAGE_SIZE >> PAGE_SHIFT;
    - if (address - vma->vm_start > current->signal->rlim[RLIMIT_STACK].rlim_cur
    - || (((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->signal->rlim[RLIMIT_AS].rlim_cur))
    - return -ENOMEM;
    - vma->vm_end += PAGE_SIZE;
    - vma->vm_mm->total_vm += grow;
    - if (vma->vm_flags & VM_LOCKED)
    - vma->vm_mm->locked_vm += grow;
    - vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file, grow);
    - return 0;
    -}
    -
    -/*
    * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
    * (inside region 5, on ia64) and that page is present.
    */
    @@ -185,7 +159,13 @@ ia64_do_page_fault (unsigned long addres
    if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
    goto bad_area;
    - if (expand_backing_store(vma, address))
    + /*
    + * Since the register backing store is accessed sequentially,
    + * we disallow growing it by more than a page at a time.
    + */
    + if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
    + goto bad_area;
    + if (expand_upwards(vma, address))
    goto bad_area;
    }
    goto good_area;
    --- mm07/arch/ia64/mm/init.c 2005-09-21 12:16:14.000000000 +0100
    +++ mm08/arch/ia64/mm/init.c 2005-10-11 23:55:38.000000000 +0100
    @@ -158,7 +158,7 @@ ia64_init_addr_space (void)
    vma->vm_start = current->thread.rbs_bot & PAGE_MASK;
    vma->vm_end = vma->vm_start + PAGE_SIZE;
    vma->vm_page_prot = protection_map[VM_DATA_DEFAULT_FLAGS & 0x7];
    - vma->vm_flags = VM_DATA_DEFAULT_FLAGS | VM_GROWSUP;
    + vma->vm_flags = VM_DATA_DEFAULT_FLAGS|VM_GROWSUP|VM_ACCOUNT;
    down_write(&current->mm->mmap_sem);
    if (insert_vm_struct(current->mm, vma)) {
    up_write(&current->mm->mmap_sem);
    --- mm07/include/linux/mm.h 2005-10-11 23:54:33.000000000 +0100
    +++ mm08/include/linux/mm.h 2005-10-11 23:55:38.000000000 +0100
    @@ -904,7 +904,8 @@ void handle_ra_miss(struct address_space
    unsigned long max_sane_readahead(unsigned long nr);

    /* Do stack extension */
    -extern int expand_stack(struct vm_area_struct * vma, unsigned long address);
    +extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
    +extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);

    /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
    extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long addr);
    --- mm07/mm/mmap.c 2005-10-11 23:54:33.000000000 +0100
    +++ mm08/mm/mmap.c 2005-10-11 23:55:38.000000000 +0100
    @@ -1504,11 +1504,15 @@ static int acct_stack_growth(struct vm_a
    return 0;
    }

    -#ifdef CONFIG_STACK_GROWSUP
    +#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
    /*
    - * vma is the first one with address > vma->vm_end. Have to extend vma.
    + * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
    + * vma is the last one with address > vma->vm_end. Have to extend vma.
    */
    -int expand_stack(struct vm_area_struct * vma, unsigned long address)
    +#ifdef CONFIG_STACK_GROWSUP
    +static inline
    +#endif
    +int expand_upwards(struct vm_area_struct *vma, unsigned long address)
    {
    int error;

    @@ -1546,6 +1550,13 @@ int expand_stack(struct vm_area_struct *
    anon_vma_unlock(vma);
    return error;
    }
    +#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
    +
    +#ifdef CONFIG_STACK_GROWSUP
    +int expand_stack(struct vm_area_struct *vma, unsigned long address)
    +{
    + return expand_upwards(vma, address);
    +}

    struct vm_area_struct *
    find_extend_vma(struct mm_struct *mm, unsigned long addr)
    -
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