Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target...

[cascardo/linux.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index f9628e5..22e037e 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2180,6 +2180,42 @@ oom:
        return VM_FAULT_OOM;
 }
 
+/*
+ * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
+ * mapping
+ */
+static int wp_pfn_shared(struct mm_struct *mm,
+                       struct vm_area_struct *vma, unsigned long address,
+                       pte_t *page_table, spinlock_t *ptl, pte_t orig_pte,
+                       pmd_t *pmd)
+{
+       if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
+               struct vm_fault vmf = {
+                       .page = NULL,
+                       .pgoff = linear_page_index(vma, address),
+                       .virtual_address = (void __user *)(address & PAGE_MASK),
+                       .flags = FAULT_FLAG_WRITE | FAULT_FLAG_MKWRITE,
+               };
+               int ret;
+
+               pte_unmap_unlock(page_table, ptl);
+               ret = vma->vm_ops->pfn_mkwrite(vma, &vmf);
+               if (ret & VM_FAULT_ERROR)
+                       return ret;
+               page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+               /*
+                * We might have raced with another page fault while we
+                * released the pte_offset_map_lock.
+                */
+               if (!pte_same(*page_table, orig_pte)) {
+                       pte_unmap_unlock(page_table, ptl);
+                       return 0;
+               }
+       }
+       return wp_page_reuse(mm, vma, address, page_table, ptl, orig_pte,
+                            NULL, 0, 0);
+}
+
 static int wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
                          unsigned long address, pte_t *page_table,
                          pmd_t *pmd, spinlock_t *ptl, pte_t orig_pte,
@@ -2258,13 +2294,12 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 * VM_PFNMAP VMA.
                 *
                 * We should not cow pages in a shared writeable mapping.
-                * Just mark the pages writable as we can't do any dirty
-                * accounting on raw pfn maps.
+                * Just mark the pages writable and/or call ops->pfn_mkwrite.
                 */
                if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
                                     (VM_WRITE|VM_SHARED))
-                       return wp_page_reuse(mm, vma, address, page_table, ptl,
-                                            orig_pte, old_page, 0, 0);
+                       return wp_pfn_shared(mm, vma, address, page_table, ptl,
+                                            orig_pte, pmd);
 
                pte_unmap_unlock(page_table, ptl);
                return wp_page_copy(mm, vma, address, page_table, pmd,