[PATCH] ext4: serialize unlocked dio reads with truncate

[Dmitry Monakhov <dmonakhov@openvz.org>]

Current serialization will works only for DIO which holds
i_mutex, but nonlocked DIO following race is possable:

dio_nolock_read_task            truncate_task
				->ext4_setattr()
				 ->inode_dio_wait()
->ext4_ext_direct_IO
  ->ext4_ind_direct_IO
    ->__blockdev_direct_IO
      ->ext4_get_block
				 ->truncate_setsize()
				 ->ext4_truncate()
				 #alloc truncated blocks
				 #to other inode
      ->submit_io()
     #INFORMATION LEAK

In order to serialize with unlocked DIO reads we have to
rearange wait sequance
1) update i_size first
2) wait for outstanding DIO requests
3) and only after that truncate inode blocks

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ext4/inode.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index d12d30e..ee534ab 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4304,8 +4304,6 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
 	}
 
 	if (attr->ia_valid & ATTR_SIZE) {
-		inode_dio_wait(inode);