[PATCH] ocfs2: Fix oops when racing files truncates with writes into an mmap region

This patch fixes an oops that is reproduced when one races writes to a mmap-ed
region with another process truncating the file.
Signed-off-by: NSunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: NMark Fasheh <mfasheh@suse.com>

fs/ocfs2/aops.c

@@ -1073,13 +1073,16 @@ static void ocfs2_write_failure(struct inode *inode,
 	for(i = 0; i < wc->w_num_pages; i++) {
 		tmppage = wc->w_pages[i];
 
+		if (page_has_buffers(tmppage)) {
 			if (ocfs2_should_order_data(inode))
-			walk_page_buffers(wc->w_handle, page_buffers(tmppage),
+				walk_page_buffers(wc->w_handle,
+						  page_buffers(tmppage),
 						  from, to, NULL,
 						  ocfs2_journal_dirty_data);
 
 			block_commit_write(tmppage, from, to);
 		}
+	}
 }
 
 static int ocfs2_prepare_page_for_write(struct inode *inode, u64 *p_blkno,
@@ -1901,13 +1904,15 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
 			to = PAGE_CACHE_SIZE;
 		}
 
+		if (page_has_buffers(tmppage)) {
 			if (ocfs2_should_order_data(inode))
-			walk_page_buffers(wc->w_handle, page_buffers(tmppage),
+				walk_page_buffers(wc->w_handle,
+						  page_buffers(tmppage),
 						  from, to, NULL,
 						  ocfs2_journal_dirty_data);
-
 			block_commit_write(tmppage, from, to);
 		}
+	}
 
 out_write_size:
 	pos += copied;