1 files changed, 19 insertions, 50 deletions

diff --git a/mm/memory.c b/mm/memory.c
index aa8af0e20269..d22f78c8a381 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -349,6 +349,11 @@ void print_bad_pte(struct vm_area_struct *vma, pte_t pte, unsigned long vaddr)
         dump_stack();
 }
 
+static inline int is_cow_mapping(unsigned int flags)
+{
+        return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+}
+
 /*
  * This function gets the "struct page" associated with a pte.
  *
@@ -377,6 +382,8 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, pte_
                 unsigned long off = (addr - vma->vm_start) >> PAGE_SHIFT;
                 if (pfn == vma->vm_pgoff + off)
                         return NULL;
+                if (!is_cow_mapping(vma->vm_flags))
+                        return NULL;
         }
 
         /*
@@ -437,7 +444,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
          * If it's a COW mapping, write protect it both
          * in the parent and the child
          */
-        if ((vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE) {
+        if (is_cow_mapping(vm_flags)) {
                 ptep_set_wrprotect(src_mm, addr, src_pte);
                 pte = *src_pte;
         }
@@ -1002,7 +1009,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         continue;
                 }
 
-                if (!vma || (vma->vm_flags & VM_IO)
+                if (!vma || (vma->vm_flags & (VM_IO | VM_PFNMAP))
                                 || !(vm_flags & vma->vm_flags))
                         return i ? : -EFAULT;
 
@@ -1226,50 +1233,6 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, struct page *
 EXPORT_SYMBOL(vm_insert_page);
 
 /*
- * Somebody does a pfn remapping that doesn't actually work as a vma.
- *
- * Do it as individual pages instead, and warn about it. It's bad form,
- * and very inefficient.
- */
-static int incomplete_pfn_remap(struct vm_area_struct *vma,
-                unsigned long start, unsigned long end,
-                unsigned long pfn, pgprot_t prot)
-{
-        static int warn = 10;
-        struct page *page;
-        int retval;
-
-        if (!(vma->vm_flags & VM_INCOMPLETE)) {
-                if (warn) {
-                        warn--;
-                        printk("%s does an incomplete pfn remapping", current->comm);
-                        dump_stack();
-                }
-        }
-        vma->vm_flags |= VM_INCOMPLETE | VM_IO | VM_RESERVED;
-
-        if (start < vma->vm_start || end > vma->vm_end)
-                return -EINVAL;
-
-        if (!pfn_valid(pfn))
-                return -EINVAL;
-
-        page = pfn_to_page(pfn);
-        if (!PageReserved(page))
-                return -EINVAL;
-
-        retval = 0;
-        while (start < end) {
-                retval = insert_page(vma->vm_mm, start, page, prot);
-                if (retval < 0)
-                        break;
-                start += PAGE_SIZE;
-                page++;
-        }
-        return retval;
-}
-
-/*
  * maps a range of physical memory into the requested pages. the old
  * mappings are removed. any references to nonexistent pages results
  * in null mappings (currently treated as "copy-on-access")
@@ -1343,9 +1306,6 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
         struct mm_struct *mm = vma->vm_mm;
         int err;
 
-        if (addr != vma->vm_start || end != vma->vm_end)
-                return incomplete_pfn_remap(vma, addr, end, pfn, prot);
-
         /*
          * Physically remapped pages are special. Tell the
          * rest of the world about it:
@@ -1359,9 +1319,18 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
          *   VM_PFNMAP tells the core MM that the base pages are just
          *      raw PFN mappings, and do not have a "struct page" associated
          *      with them.
+         *
+         * There's a horrible special case to handle copy-on-write
+         * behaviour that some programs depend on. We mark the "original"
+         * un-COW'ed pages by matching them up with "vma->vm_pgoff".
          */
+        if (is_cow_mapping(vma->vm_flags)) {
+                if (addr != vma->vm_start || end != vma->vm_end)
+                        return -EINVAL;
+                vma->vm_pgoff = pfn;
+        }
+
         vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
-        vma->vm_pgoff = pfn;
 
         BUG_ON(addr >= end);
         pfn -= addr >> PAGE_SHIFT;