1 files changed, 25 insertions, 20 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 4bad3267537a..0feeef860a8f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -133,8 +133,8 @@ int anon_vma_prepare(struct vm_area_struct *vma)
                                 goto out_enomem_free_avc;
                         allocated = anon_vma;
                 }
-                spin_lock(&anon_vma->lock);
 
+                spin_lock(&anon_vma->lock);
                 /* page_table_lock to protect against threads */
                 spin_lock(&mm->page_table_lock);
                 if (likely(!vma->anon_vma)) {
@@ -144,14 +144,15 @@ int anon_vma_prepare(struct vm_area_struct *vma)
                         list_add(&avc->same_vma, &vma->anon_vma_chain);
                         list_add(&avc->same_anon_vma, &anon_vma->head);
                         allocated = NULL;
+                        avc = NULL;
                 }
                 spin_unlock(&mm->page_table_lock);
-
                 spin_unlock(&anon_vma->lock);
-                if (unlikely(allocated)) {
+
+                if (unlikely(allocated))
                         anon_vma_free(allocated);
+                if (unlikely(avc))
                         anon_vma_chain_free(avc);
-                }
         }
         return 0;
 
@@ -335,14 +336,13 @@ vma_address(struct page *page, struct vm_area_struct *vma)
 
 /*
  * At what user virtual address is page expected in vma?
- * checking that the page matches the vma.
+ * Caller should check the page is actually part of the vma.
  */
 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 {
-        if (PageAnon(page)) {
-                if (vma->anon_vma != page_anon_vma(page))
-                        return -EFAULT;
-        } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
+        if (PageAnon(page))
+                ;
+        else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
                 if (!vma->vm_file ||
                     vma->vm_file->f_mapping != page->mapping)
                         return -EFAULT;
@@ -730,23 +730,28 @@ void page_move_anon_rmap(struct page *page,
  * @page:       the page to add the mapping to
  * @vma:        the vm area in which the mapping is added
  * @address:    the user virtual address mapped
+ * @exclusive:  the page is exclusively owned by the current process
  */
 static void __page_set_anon_rmap(struct page *page,
-        struct vm_area_struct *vma, unsigned long address)
+        struct vm_area_struct *vma, unsigned long address, int exclusive)
 {
-        struct anon_vma_chain *avc;
-        struct anon_vma *anon_vma;
+        struct anon_vma *anon_vma = vma->anon_vma;
 
-        BUG_ON(!vma->anon_vma);
+        BUG_ON(!anon_vma);
 
         /*
-         * We must use the _oldest_ possible anon_vma for the page mapping!
+         * If the page isn't exclusively mapped into this vma,
+         * we must use the _oldest_ possible anon_vma for the
+         * page mapping!
          *
-         * So take the last AVC chain entry in the vma, which is the deepest
-         * ancestor, and use the anon_vma from that.
+         * So take the last AVC chain entry in the vma, which is
+         * the deepest ancestor, and use the anon_vma from that.
          */
-        avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
-        anon_vma = avc->anon_vma;
+        if (!exclusive) {
+                struct anon_vma_chain *avc;
+                avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
+                anon_vma = avc->anon_vma;
+        }
 
         anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
         page->mapping = (struct address_space *) anon_vma;
@@ -802,7 +807,7 @@ void page_add_anon_rmap(struct page *page,
         VM_BUG_ON(!PageLocked(page));
         VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
         if (first)
-                __page_set_anon_rmap(page, vma, address);
+                __page_set_anon_rmap(page, vma, address, 0);
         else
                 __page_check_anon_rmap(page, vma, address);
 }
@@ -824,7 +829,7 @@ void page_add_new_anon_rmap(struct page *page,
         SetPageSwapBacked(page);
         atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
         __inc_zone_page_state(page, NR_ANON_PAGES);
-        __page_set_anon_rmap(page, vma, address);
+        __page_set_anon_rmap(page, vma, address, 1);
         if (page_evictable(page, vma))
                 lru_cache_add_lru(page, LRU_ACTIVE_ANON);
         else