ext4: avoid potential hang in mpage_submit_io() when blocksize < pagesize

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>
Cc: stable@kernel.org

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b5edc6e..cf20e1f 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1339,8 +1339,11 @@ 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;