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    Subject[RFC PATCH 01/33] Add apply_to_page_range() function
    Add a new mm function apply_to_page_range() which applies a given
    function to every pte in a given virtual address range in a given mm
    structure. This is a generic alternative to cut-and-pasting the Linux
    idiomatic pagetable walking code in every place that a sequence of
    PTEs must be accessed.

    Although this interface is intended to be useful in a wide range of
    situations, it is currently used specifically by several Xen
    subsystems, for example: to ensure that pagetables have been allocated
    for a virtual address range, and to construct batched special
    pagetable update requests to map I/O memory (in ioremap()).

    Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
    Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
    Signed-off-by: Chris Wright <chrisw@sous-sol.org>
    ---
    include/linux/mm.h | 5 ++
    mm/memory.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 99 insertions(+)

    diff -r 84a7a7b38774 include/linux/mm.h
    --- a/include/linux/mm.h Fri Mar 24 04:29:46 2006 +0000
    +++ b/include/linux/mm.h Fri Mar 24 04:30:48 2006 +0000
    @@ -1013,6 +1013,11 @@ struct page *follow_page(struct vm_area_
    #define FOLL_GET 0x04 /* do get_page on page */
    #define FOLL_ANON 0x08 /* give ZERO_PAGE if no pgtable */

    +typedef int (*pte_fn_t)(pte_t *pte, struct page *pmd_page, unsigned long addr,
    + void *data);
    +extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
    + unsigned long size, pte_fn_t fn, void *data);
    +
    #ifdef CONFIG_PROC_FS
    void vm_stat_account(struct mm_struct *, unsigned long, struct file *, long);
    #else
    diff -r 84a7a7b38774 mm/memory.c
    --- a/mm/memory.c Fri Mar 24 04:29:46 2006 +0000
    +++ b/mm/memory.c Fri Mar 24 04:30:48 2006 +0000
    @@ -1358,6 +1358,100 @@ int remap_pfn_range(struct vm_area_struc
    }
    EXPORT_SYMBOL(remap_pfn_range);

    +static inline int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
    + unsigned long addr, unsigned long end,
    + pte_fn_t fn, void *data)
    +{
    + pte_t *pte;
    + int err;
    + struct page *pmd_page;
    + spinlock_t *ptl;
    +
    + pte = (mm == &init_mm) ?
    + pte_alloc_kernel(pmd, addr) :
    + pte_alloc_map_lock(mm, pmd, addr, &ptl);
    + if (!pte)
    + return -ENOMEM;
    +
    + BUG_ON(pmd_huge(*pmd));
    +
    + pmd_page = pmd_page(*pmd);
    +
    + do {
    + err = fn(pte, pmd_page, addr, data);
    + if (err)
    + break;
    + } while (pte++, addr += PAGE_SIZE, addr != end);
    +
    + if (mm != &init_mm)
    + pte_unmap_unlock(pte-1, ptl);
    + return err;
    +}
    +
    +static inline int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
    + unsigned long addr, unsigned long end,
    + pte_fn_t fn, void *data)
    +{
    + pmd_t *pmd;
    + unsigned long next;
    + int err;
    +
    + pmd = pmd_alloc(mm, pud, addr);
    + if (!pmd)
    + return -ENOMEM;
    + do {
    + next = pmd_addr_end(addr, end);
    + err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
    + if (err)
    + break;
    + } while (pmd++, addr = next, addr != end);
    + return err;
    +}
    +
    +static inline int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
    + unsigned long addr, unsigned long end,
    + pte_fn_t fn, void *data)
    +{
    + pud_t *pud;
    + unsigned long next;
    + int err;
    +
    + pud = pud_alloc(mm, pgd, addr);
    + if (!pud)
    + return -ENOMEM;
    + do {
    + next = pud_addr_end(addr, end);
    + err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
    + if (err)
    + break;
    + } while (pud++, addr = next, addr != end);
    + return err;
    +}
    +
    +/*
    + * Scan a region of virtual memory, filling in page tables as necessary
    + * and calling a provided function on each leaf page table.
    + */
    +int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
    + unsigned long size, pte_fn_t fn, void *data)
    +{
    + pgd_t *pgd;
    + unsigned long next;
    + unsigned long end = addr + size;
    + int err;
    +
    + BUG_ON(addr >= end);
    + pgd = pgd_offset(mm, addr);
    + do {
    + next = pgd_addr_end(addr, end);
    + err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
    + if (err)
    + break;
    + } while (pgd++, addr = next, addr != end);
    + return err;
    +}
    +EXPORT_SYMBOL_GPL(apply_to_page_range);
    +
    /*
    * handle_pte_fault chooses page fault handler according to an entry
    * which was read non-atomically. Before making any commitment, on
    --
    -
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