Description of problem:
 I create a disperse 3 redundancy 1 volume, then touch /mountpoint/file.txt. I execute "echo 'AAAAAAAAAAAAAAAAAA' >> /mountpoint/file.txt", no error report, then read /mountpoint/file.txt by cat is NULL.But I can read the "AAAAAAAAAAAAAAA" from sub-directory's file.txt by cat.

  file.txt's size is ok,  echo "AAAAAAAAAAA" > /mountpointf/file.txt (OVERWRITE) and copy all are ok.
  

  
Version-Release number of selected component (if applicable):
3.6.0 and 3.6.1 and glusterfs-master from git

How reproducible:


Steps to Reproduce:
1.create a disperse 3 redundancy 1 volume
Volume Name: test
Type: Disperse
Volume ID: 5de6b5d7-dc4f-48c6-bc2b-15019c900ed2
Status: Started
Number of Bricks: 1 x (2 + 1) = 3
Transport-type: tcp
Bricks:
Brick1: 10.10.21.50:/sda
Brick2: 10.10.21.50:/sdb
Brick3: 10.10.21.50:/sdc

2.touch /mountpoint/file.txt
3.echo "AAAAAAAAAAAAAAA" >> /mountpoint/file.txt (APEND)
4.Can not read strings from /mountpoint/file.txt (by cat)

Actual results:


Expected results:


Additional info:

In my opinion, the circuit of O_APEND write is abnormal  in disperse.