1 files changed, 42 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index d2b5be9f..17fd1bc0 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2930,6 +2930,48 @@ EXPORT_SYMBOL(block_truncate_page);
 
 /*
  * The generic ->writepage function for buffer-backed address_spaces
+ * this form passes in the end_io handler used to finish the IO.
+ */
+int block_write_full_page_endio(struct page *page, get_block_t *get_block,
+			struct writeback_control *wbc, bh_end_io_t *handler)
+{
+	struct inode * const inode = page->mapping->host;
+	loff_t i_size = i_size_read(inode);
+	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
+	unsigned offset;
+
+	/* Is the page fully inside i_size? */
+	if (page->index < end_index)
+		return __block_write_full_page(inode, page, get_block, wbc,
+					       handler);
+
+	/* Is the page fully outside i_size? (truncate in progress) */
+	offset = i_size & (PAGE_CACHE_SIZE-1);
+	if (page->index >= end_index+1 || !offset) {
+		/*
+		 * The page may have dirty, unmapped buffers.  For example,
+		 * they may have been added in ext3_writepage().  Make them
+		 * freeable here, so the page does not leak.
+		 */
+		do_invalidatepage(page, 0,PAGE_CACHE_SIZE);
+		unlock_page(page);
+		return 0; /* don't care */
+	}
+
+	/*
+	 * The page straddles i_size.  It must be zeroed out on each and every
+	 * writepage invocation because it may be mmapped.  "A file is mapped
+	 * in multiples of the page size.  For a file that is not a multiple of
+	 * the  page size, the remaining memory is zeroed when mapped, and
+	 * writes to that region are not written out to the file."
+	 */
+	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
+	return __block_write_full_page(inode, page, get_block, wbc, handler);
+}
+EXPORT_SYMBOL(block_write_full_page_endio);
+
+/*
+ * The generic ->writepage function for buffer-backed address_spaces
  */
 int block_write_full_page(struct page *page, get_block_t *get_block,
 			struct writeback_control *wbc)