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    DateTue, 21 Mar 2006 22:31:10 -0800
    FromChris Wright <>
    Subject[RFC PATCH 30/35] Add generic_page_range() function
    Add a new mm function generic_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        |   90 +++++++++++++++++++++++++++++++++++++++++++++++++++++
     2 files changed, 95 insertions(+)
    --- xen-subarch-2.6.orig/include/linux/mm.h
    +++ xen-subarch-2.6/include/linux/mm.h
    @@ -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 *pte_page, unsigned long addr,
    +                        void *data);
    +extern int generic_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
    --- xen-subarch-2.6.orig/mm/memory.c
    +++ xen-subarch-2.6/mm/memory.c
    @@ -1359,6 +1359,96 @@ int remap_pfn_range(struct vm_area_struc
     }
     EXPORT_SYMBOL(remap_pfn_range);
     
    +static inline int generic_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 *pte_page;
    +
    +	pte = (mm == &init_mm) ?
    +		pte_alloc_kernel(pmd, addr) :
    +		pte_alloc_map(mm, pmd, addr);
    +	if (!pte)
    +		return -ENOMEM;
    +
    +	pte_page = pmd_page(*pmd);
    +
    +	do {
    +		err = fn(pte, pte_page, addr, data);
    +		if (err)
    +			break;
    +	} while (pte++, addr += PAGE_SIZE, addr != end);
    +
    +	if (mm != &init_mm)
    +		pte_unmap(pte-1);
    +	return err;
    +}
    +
    +static inline int generic_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 = generic_pte_range(mm, pmd, addr, next, fn, data);
    +		if (err)
    +			break;
    +	} while (pmd++, addr = next, addr != end);
    +	return err;
    +}
    +
    +static inline int generic_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 = generic_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 generic_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 = generic_pud_range(mm, pgd, addr, next, fn, data);
    +		if (err)
    +			break;
    +	} while (pgd++, addr = next, addr != end);
    +	return err;
    +}
    +
     /*
      * 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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