From 8fe5e8ff93473129957c6d4a7df80046186b9c7b Mon Sep 17 00:00:00 2001
From: Yongqiang Yang <xiaoqiangnk@gmail.com>
Date: Tue, 13 Dec 2011 21:51:55 -0500
Subject: ext4: avoid potential hang in mpage_submit_io() when blocksize <
 pagesize

commit 13a79a4741d37fda2fbafb953f0f301dc007928f upstream.

If there is an unwritten but clean buffer in a page and there is a
dirty buffer after the buffer, then mpage_submit_io does not write the
dirty buffer out.  As a result, da_writepages loops forever.

This patch fixes the problem by checking dirty flag.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 fs/ext4/inode.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ea9076b8d91..af0906080fd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2126,8 +2126,11 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
 					clear_buffer_unwritten(bh);
 				}
 
-				/* skip page if block allocation undone */
-				if (buffer_delay(bh) || buffer_unwritten(bh))
+				/*
+				 * skip page if block allocation undone and
+				 * block is dirty
+				 */
+				if (ext4_bh_delay_or_unwritten(NULL, bh))
 					skip_page = 1;
 				bh = bh->b_this_page;
 				block_start += bh->b_size;
-- 
cgit v1.2.3-18-g5258