mm + fs: store shadow entries in page cache

[deliverable/linux.git] / mm / filemap.c

diff --git a/mm/filemap.c b/mm/filemap.c
index efc63876477f7fefcdf7de94309bf62448f11687..05c44aa44188e8dbb5fe62c342bd8c63cdd2f4b5 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -107,12 +107,33 @@
  *   ->tasklist_lock            (memory_failure, collect_procs_ao)
  */
 
+static void page_cache_tree_delete(struct address_space *mapping,
+                                  struct page *page, void *shadow)
+{
+       if (shadow) {
+               void **slot;
+
+               slot = radix_tree_lookup_slot(&mapping->page_tree, page->index);
+               radix_tree_replace_slot(slot, shadow);
+               mapping->nrshadows++;
+               /*
+                * Make sure the nrshadows update is committed before
+                * the nrpages update so that final truncate racing
+                * with reclaim does not see both counters 0 at the
+                * same time and miss a shadow entry.
+                */
+               smp_wmb();
+       } else
+               radix_tree_delete(&mapping->page_tree, page->index);
+       mapping->nrpages--;
+}
+
 /*
  * Delete a page from the page cache and free it. Caller has to make
  * sure the page is locked and that nobody else uses it - or that usage
  * is safe.  The caller must hold the mapping's tree_lock.
  */
-void __delete_from_page_cache(struct page *page)
+void __delete_from_page_cache(struct page *page, void *shadow)
 {
        struct address_space *mapping = page->mapping;
 
@@ -127,10 +148,11 @@ void __delete_from_page_cache(struct page *page)
        else
                cleancache_invalidate_page(mapping, page);
 
-       radix_tree_delete(&mapping->page_tree, page->index);
+       page_cache_tree_delete(mapping, page, shadow);
+
        page->mapping = NULL;
        /* Leave page->index set: truncation lookup relies upon it */
-       mapping->nrpages--;
+
        __dec_zone_page_state(page, NR_FILE_PAGES);
        if (PageSwapBacked(page))
                __dec_zone_page_state(page, NR_SHMEM);
@@ -166,7 +188,7 @@ void delete_from_page_cache(struct page *page)
 
        freepage = mapping->a_ops->freepage;
        spin_lock_irq(&mapping->tree_lock);
-       __delete_from_page_cache(page);
+       __delete_from_page_cache(page, NULL);
        spin_unlock_irq(&mapping->tree_lock);
        mem_cgroup_uncharge_cache_page(page);
 
@@ -426,7 +448,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
                new->index = offset;
 
                spin_lock_irq(&mapping->tree_lock);
-               __delete_from_page_cache(old);
+               __delete_from_page_cache(old, NULL);
                error = radix_tree_insert(&mapping->page_tree, offset, new);
                BUG_ON(error);
                mapping->nrpages++;
@@ -460,6 +482,7 @@ static int page_cache_tree_insert(struct address_space *mapping,
                if (!radix_tree_exceptional_entry(p))
                        return -EEXIST;
                radix_tree_replace_slot(slot, page);
+               mapping->nrshadows--;
                mapping->nrpages++;
                return 0;
        }