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-rw-r--r--mm/filemap.c33
1 files changed, 28 insertions, 5 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index efc63876477f..05c44aa44188 100644
--- 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;
}