1 files changed, 45 insertions, 11 deletions

diff --git a/mm/memory.c b/mm/memory.c
index ac20b2a6a0c3..22e037e3364e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -690,12 +690,11 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
         /*
          * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
          */
-        if (vma->vm_ops)
-                printk(KERN_ALERT "vma->vm_ops->fault: %pSR\n",
-                       vma->vm_ops->fault);
-        if (vma->vm_file)
-                printk(KERN_ALERT "vma->vm_file->f_op->mmap: %pSR\n",
-                       vma->vm_file->f_op->mmap);
+        pr_alert("file:%pD fault:%pf mmap:%pf readpage:%pf\n",
+                 vma->vm_file,
+                 vma->vm_ops ? vma->vm_ops->fault : NULL,
+                 vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
+                 mapping ? mapping->a_ops->readpage : NULL);
         dump_stack();
         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
@@ -2181,6 +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,
@@ -2259,13 +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,
@@ -2845,7 +2879,7 @@ static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
         struct vm_fault vmf;
         int off;
 
-        nr_pages = ACCESS_ONCE(fault_around_bytes) >> PAGE_SHIFT;
+        nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;
         mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;
 
         start_addr = max(address & mask, vma->vm_start);