mm: refactor do_wp_page handling of shared vma into a function

The do_wp_page function is extremely long.  Extract the logic for
handling a page belonging to a shared vma into a function of its own.

This helps the readability of the code, without doing any functional
change in it.

Signed-off-by: Shachar Raindel <raindel@mellanox.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Haggai Eran <haggaie@mellanox.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: Michel Lespinasse <walken@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
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 cfd3c78..ac20b2a 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2181,6 +2181,52 @@ oom:
        return VM_FAULT_OOM;
 }
 
+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,
+                         struct page *old_page)
+       __releases(ptl)
+{
+       int page_mkwrite = 0;
+
+       page_cache_get(old_page);
+
+       /*
+        * Only catch write-faults on shared writable pages,
+        * read-only shared pages can get COWed by
+        * get_user_pages(.write=1, .force=1).
+        */
+       if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
+               int tmp;
+
+               pte_unmap_unlock(page_table, ptl);
+               tmp = do_page_mkwrite(vma, old_page, address);
+               if (unlikely(!tmp || (tmp &
+                                     (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+                       page_cache_release(old_page);
+                       return tmp;
+               }
+               /*
+                * Since we dropped the lock we need to revalidate
+                * the PTE as someone else may have changed it.  If
+                * they did, we just return, as we can count on the
+                * MMU to tell us if they didn't also make it writable.
+                */
+               page_table = pte_offset_map_lock(mm, pmd, address,
+                                                &ptl);
+               if (!pte_same(*page_table, orig_pte)) {
+                       unlock_page(old_page);
+                       pte_unmap_unlock(page_table, ptl);
+                       page_cache_release(old_page);
+                       return 0;
+               }
+               page_mkwrite = 1;
+       }
+
+       return wp_page_reuse(mm, vma, address, page_table, ptl,
+                            orig_pte, old_page, page_mkwrite, 1);
+}
+
 /*
  * This routine handles present pages, when users try to write
  * to a shared page. It is done by copying the page to a new address
@@ -2259,44 +2305,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                unlock_page(old_page);
        } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
                                        (VM_WRITE|VM_SHARED))) {
-               int page_mkwrite = 0;
-
-               page_cache_get(old_page);
-
-               /*
-                * Only catch write-faults on shared writable pages,
-                * read-only shared pages can get COWed by
-                * get_user_pages(.write=1, .force=1).
-                */
-               if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
-                       int tmp;
-
-                       pte_unmap_unlock(page_table, ptl);
-                       tmp = do_page_mkwrite(vma, old_page, address);
-                       if (unlikely(!tmp || (tmp &
-                                       (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
-                               page_cache_release(old_page);
-                               return tmp;
-                       }
-                       /*
-                        * Since we dropped the lock we need to revalidate
-                        * the PTE as someone else may have changed it.  If
-                        * they did, we just return, as we can count on the
-                        * MMU to tell us if they didn't also make it writable.
-                        */
-                       page_table = pte_offset_map_lock(mm, pmd, address,
-                                                        &ptl);
-                       if (!pte_same(*page_table, orig_pte)) {
-                               unlock_page(old_page);
-                               pte_unmap_unlock(page_table, ptl);
-                               page_cache_release(old_page);
-                               return 0;
-                       }
-                       page_mkwrite = 1;
-               }
-
-               return wp_page_reuse(mm, vma, address, page_table, ptl,
-                                    orig_pte, old_page, page_mkwrite, 1);
+               return wp_page_shared(mm, vma, address, page_table, pmd,
+                                     ptl, orig_pte, old_page);
        }
 
        /*