mm: factor out common parts of write fault handling

Currently we duplicate handling of shared write faults in
wp_page_reuse() and do_shared_fault().  Factor them out into a common
function.

Link: http://lkml.kernel.org/r/1479460644-25076-12-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index ca3b95f..6fd8278 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2063,6 +2063,41 @@ static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page,
 }
 
 /*
+ * Handle dirtying of a page in shared file mapping on a write fault.
+ *
+ * The function expects the page to be locked and unlocks it.
+ */
+static void fault_dirty_shared_page(struct vm_area_struct *vma,
+                                   struct page *page)
+{
+       struct address_space *mapping;
+       bool dirtied;
+       bool page_mkwrite = vma->vm_ops && vma->vm_ops->page_mkwrite;
+
+       dirtied = set_page_dirty(page);
+       VM_BUG_ON_PAGE(PageAnon(page), page);
+       /*
+        * Take a local copy of the address_space - page.mapping may be zeroed
+        * by truncate after unlock_page().   The address_space itself remains
+        * pinned by vma->vm_file's reference.  We rely on unlock_page()'s
+        * release semantics to prevent the compiler from undoing this copying.
+        */
+       mapping = page_rmapping(page);
+       unlock_page(page);
+
+       if ((dirtied || page_mkwrite) && mapping) {
+               /*
+                * Some device drivers do not set page.mapping
+                * but still dirty their pages
+                */
+               balance_dirty_pages_ratelimited(mapping);
+       }
+
+       if (!page_mkwrite)
+               file_update_time(vma->vm_file);
+}
+
+/*
  * Handle write page faults for pages that can be reused in the current vma
  *
  * This can happen either due to the mapping being with the VM_SHARED flag,
@@ -2092,28 +2127,11 @@ static inline int wp_page_reuse(struct vm_fault *vmf, struct page *page,
        pte_unmap_unlock(vmf->pte, vmf->ptl);
 
        if (dirty_shared) {
-               struct address_space *mapping;
-               int dirtied;
-
                if (!page_mkwrite)
                        lock_page(page);
 
-               dirtied = set_page_dirty(page);
-               VM_BUG_ON_PAGE(PageAnon(page), page);
-               mapping = page->mapping;
-               unlock_page(page);
+               fault_dirty_shared_page(vma, page);
                put_page(page);
-
-               if ((dirtied || page_mkwrite) && mapping) {
-                       /*
-                        * Some device drivers do not set page.mapping
-                        * but still dirty their pages
-                        */
-                       balance_dirty_pages_ratelimited(mapping);
-               }
-
-               if (!page_mkwrite)
-                       file_update_time(vma->vm_file);
        }
 
        return VM_FAULT_WRITE;
@@ -3294,8 +3312,6 @@ uncharge_out:
 static int do_shared_fault(struct vm_fault *vmf)
 {
        struct vm_area_struct *vma = vmf->vma;
-       struct address_space *mapping;
-       int dirtied = 0;
        int ret, tmp;
 
        ret = __do_fault(vmf);
@@ -3324,27 +3340,7 @@ static int do_shared_fault(struct vm_fault *vmf)
                return ret;
        }
 
-       if (set_page_dirty(vmf->page))
-               dirtied = 1;
-       /*
-        * Take a local copy of the address_space - page.mapping may be zeroed
-        * by truncate after unlock_page().   The address_space itself remains
-        * pinned by vma->vm_file's reference.  We rely on unlock_page()'s
-        * release semantics to prevent the compiler from undoing this copying.
-        */
-       mapping = page_rmapping(vmf->page);
-       unlock_page(vmf->page);
-       if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
-               /*
-                * Some device drivers do not set page.mapping but still
-                * dirty their pages
-                */
-               balance_dirty_pages_ratelimited(mapping);
-       }
-
-       if (!vma->vm_ops->page_mkwrite)
-               file_update_time(vma->vm_file);
-
+       fault_dirty_shared_page(vma, vmf->page);
        return ret;
 }