[patch 4/5] mm: add vm_insert_pfn helpler

Nick Piggin
2006-10-10T14:22:14Z

Add a vm_insert_pfn helper, so that ->fault handlers can have nopfn
functionality by installing their own pte and returning NULL.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h
+++ linux-2.6/include/linux/mm.h
@@ -1121,6 +1121,7 @@ unsigned long vmalloc_to_pfn(void *addr)
int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t);
int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
+int vm_insert_pfn(struct vm_area_struct *, unsigned long addr, unsigned long pfn);

struct page *follow_page(struct vm_area_struct *, unsigned long address,
unsigned int foll_flags);
Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c
+++ linux-2.6/mm/memory.c
@@ -1267,6 +1267,50 @@ int vm_insert_page(struct vm_area_struct
}
EXPORT_SYMBOL(vm_insert_page);

+/**
+ * vm_insert_pfn - insert single pfn into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pfn: source kernel pfn
+ *
+ * Similar to vm_inert_page, this allows drivers to insert individual pages
+ * they've allocated into a user vma. Same comments apply.
+ *
+ * This function should only be called from a vm_ops->fault handler, and
+ * in that case the handler should return NULL.
+ */
+int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ int retval;
+ pte_t *pte, entry;
+ spinlock_t *ptl;
+
+ BUG_ON(!(vma->vm_flags & VM_PFNMAP));
+ BUG_ON(is_cow_mapping(vma->vm_flags));
+
+ retval = -ENOMEM;
+ pte = get_locked_pte(mm, addr, &ptl);
+ if (!pte)
+ goto out;
+ retval = -EBUSY;
+ if (!pte_none(*pte))
+ goto out_unlock;
+
+ /* Ok, finally just insert the thing.. */
+ entry = pfn_pte(pfn, vma->vm_page_prot);
+ set_pte_at(mm, addr, pte, entry);
+ update_mmu_cache(vma, addr, entry);
+
+ retval = 0;
+out_unlock:
+ pte_unmap_unlock(pte, ptl);
+
+out:
+ return retval;
+}
+EXPORT_SYMBOL(vm_insert_pfn);
+
/*
* maps a range of physical memory into the requested pages. the old
* mappings are removed. any references to nonexistent pages results