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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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