1 files changed, 8 insertions, 6 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index f820e600f1ad..10a171113273 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -128,6 +128,7 @@ void __delete_from_page_cache(struct page *page)
 
         radix_tree_delete(&mapping->page_tree, page->index);
         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))
@@ -483,6 +484,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                         spin_unlock_irq(&mapping->tree_lock);
                 } else {
                         page->mapping = NULL;
+                        /* Leave page->index set: truncation relies upon it */
                         spin_unlock_irq(&mapping->tree_lock);
                         mem_cgroup_uncharge_cache_page(page);
                         page_cache_release(page);
@@ -1792,7 +1794,7 @@ EXPORT_SYMBOL(generic_file_readonly_mmap);
 
 static struct page *__read_cache_page(struct address_space *mapping,
                                 pgoff_t index,
-                                int (*filler)(void *,struct page*),
+                                int (*filler)(void *, struct page *),
                                 void *data,
                                 gfp_t gfp)
 {
@@ -1823,7 +1825,7 @@ repeat:
 
 static struct page *do_read_cache_page(struct address_space *mapping,
                                 pgoff_t index,
-                                int (*filler)(void *,struct page*),
+                                int (*filler)(void *, struct page *),
                                 void *data,
                                 gfp_t gfp)
 
@@ -1863,7 +1865,7 @@ out:
  * @mapping:    the page's address_space
  * @index:      the page index
  * @filler:     function to perform the read
- * @data:       destination for read data
+ * @data:       first arg to filler(data, page) function, often left as NULL
  *
  * Same as read_cache_page, but don't wait for page to become unlocked
  * after submitting it to the filler.
@@ -1875,7 +1877,7 @@ out:
  */
 struct page *read_cache_page_async(struct address_space *mapping,
                                 pgoff_t index,
-                                int (*filler)(void *,struct page*),
+                                int (*filler)(void *, struct page *),
                                 void *data)
 {
         return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
@@ -1923,7 +1925,7 @@ EXPORT_SYMBOL(read_cache_page_gfp);
  * @mapping:    the page's address_space
  * @index:      the page index
  * @filler:     function to perform the read
- * @data:       destination for read data
+ * @data:       first arg to filler(data, page) function, often left as NULL
  *
  * Read into the page cache. If a page already exists, and PageUptodate() is
  * not set, try to fill the page then wait for it to become unlocked.
@@ -1932,7 +1934,7 @@ EXPORT_SYMBOL(read_cache_page_gfp);
  */
 struct page *read_cache_page(struct address_space *mapping,
                                 pgoff_t index,
-                                int (*filler)(void *,struct page*),
+                                int (*filler)(void *, struct page *),
                                 void *data)
 {
         return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));