Bug 1225997

+++ This bug was initially created as a clone of Bug #1221696 +++

+++ This bug was initially created as a clone of Bug #1221656 +++

Description of problem:
-----------------------
I was using 2 RHEL 6.6 machines and installed glusterfs-3.7.0beta2 builds. Each node has 3 bricks. After creating a cluster of these 2 nodes, by peer probing, I created a distributed replicate volume of 2X2 bricks.

Adding a pair of another bricks to this volume and rebalancing resulted in rebalance failing in one of the node.


Version-Release number of selected component (if applicable):
-------------------------------------------------------------
glusterfs-3.7.0beta2 build

How reproducible:
------------------
Always

Steps to Reproduce:
-------------------
1. Create a 2 node cluster with 3 bricks per node
2. Create a distributed-replicate volume of 2X2 
3. Start the volume
4. Mount the volume ( fuse, nfs )
5. Create few files on the mount
6. Add a pair of bricks to the volume
7. Perform rebalance

Actual results:
---------------
Rebalance failed on the second node

Expected results:
-----------------
Rebalance should complete successfully

--- Additional comment from SATHEESARAN on 2015-05-14 09:57:44 EDT ---

[root@~]# gluster volume rebalance vmstore start
volume rebalance: vmstore: success: Rebalance on vmstore has been started successfully. Use rebalance status command to check status of the rebalance process.
ID: 9372b71c-e6f4-44fb-a2e4-9707443f3457

[root@ ~]# gluster volume rebalance vmstore status
                                    Node Rebalanced-files          size       scanned      failures       skipped               status   run time in secs
                               ---------      -----------   -----------   -----------   -----------   -----------         ------------     --------------
                               localhost                0        0Bytes             3             0             1            completed               1.00
                             10.70.37.58                0        0Bytes             0             3             0               failed               0.00
volume rebalance: vmstore: success:

<snip_rebalance_logs>
[2015-05-14 19:17:41.419890] I [dht-rebalance.c:2112:gf_defrag_process_dir] 0-vmstore-dht: migrate data called on /
[2015-05-14 19:17:41.424661] I [dht-common.c:3539:dht_setxattr] 0-vmstore-dht: fixing the layout of /.trashcan
[2015-05-14 19:17:41.424688] I [dht-selfheal.c:1494:dht_fix_layout_of_directory] 0-vmstore-dht: subvolume 0 (vmstore-replicate-0): 101834 chunks
[2015-05-14 19:17:41.424699] I [dht-selfheal.c:1494:dht_fix_layout_of_directory] 0-vmstore-dht: subvolume 1 (vmstore-replicate-1): 101834 chunks
[2015-05-14 19:17:41.424708] I [dht-selfheal.c:1494:dht_fix_layout_of_directory] 0-vmstore-dht: subvolume 2 (vmstore-replicate-2): 101834 chunks
[2015-05-14 19:17:41.434411] I [dht-rebalance.c:2112:gf_defrag_process_dir] 0-vmstore-dht: migrate data called on /.trashcan
[2015-05-14 19:17:41.446254] I [dht-common.c:3539:dht_setxattr] 0-vmstore-dht: fixing the layout of /.trashcan/internal_op
[2015-05-14 19:17:41.446279] I [dht-selfheal.c:1494:dht_fix_layout_of_directory] 0-vmstore-dht: subvolume 0 (vmstore-replicate-0): 101834 chunks
[2015-05-14 19:17:41.446290] I [dht-selfheal.c:1494:dht_fix_layout_of_directory] 0-vmstore-dht: subvolume 1 (vmstore-replicate-1): 101834 chunks
[2015-05-14 19:17:41.446298] I [dht-selfheal.c:1494:dht_fix_layout_of_directory] 0-vmstore-dht: subvolume 2 (vmstore-replicate-2): 101834 chunks
[2015-05-14 19:17:41.453365] I [dht-rebalance.c:2112:gf_defrag_process_dir] 0-vmstore-dht: migrate data called on /.trashcan/internal_op
[2015-05-14 19:17:41.458214] I [dht-common.c:3539:dht_setxattr] 0-vmstore-dht: fixing the layout of /.trashcan/internal_op
[2015-05-14 19:17:41.458542] E [dht-rebalance.c:2368:gf_defrag_settle_hash] 0-vmstore-dht: fix layout on /.trashcan/internal_op failed
[2015-05-14 19:17:41.458824] E [MSGID: 109016] [dht-rebalance.c:2528:gf_defrag_fix_layout] 0-vmstore-dht: Fix layout failed for /.trashcan
</snip_rebalance_logs>

--- Additional comment from SATHEESARAN on 2015-05-14 09:59:17 EDT ---

Following is the mail conversation from Nithya to gluster-devel for this issue :

<snip>
The rebalance failure is due to the interaction of the lookup-unhashed changes and rebalance local crawl changes.
</snip>

--- Additional comment from Anand Avati on 2015-05-14 11:09:36 EDT ---

REVIEW: http://review.gluster.org/10786 (dht/rebalance : Fixed rebalance failure) posted (#1) for review on master by N Balachandran (nbalacha)

--- Additional comment from Anand Avati on 2015-05-14 11:17:36 EDT ---

REVIEW: http://review.gluster.org/10786 (dht/rebalance : Fixed rebalance failure) posted (#2) for review on master by N Balachandran (nbalacha)

--- Additional comment from Anand Avati on 2015-05-14 15:13:45 EDT ---

COMMIT: http://review.gluster.org/10786 committed in master by Shyamsundar Ranganathan (srangana) 
------
commit 1cabc769c7b636f89f6f28aaa0d534401a82d4a8
Author: Nithya Balachandran <nbalacha>
Date:   Thu May 14 19:33:44 2015 +0530

    dht/rebalance : Fixed rebalance failure
    
    The rebalance process determines the local subvols for the
    node it is running on and only acts on files in those subvols.
    If a dist-rep or dist-disperse volume is created on 2 nodes by
    dividing the bricks equally across the nodes, one process might
    determine it has no local_subvols.
    
    When trying to update the commit hash, the function attempts to
    lock all local subvols. On the node with no local_subvols the dht
    inode lock operation fails, in turn causing the rebalance to fail.
    
    In a dist-rep volume with 2 nodes, if brick 0 of each replica
    set is on node1 and brick 1 is on node2, node2 will find that it has
    no local subvols.
    
    Change-Id: I7d73b5b4bf1c822eae6df2e6f79bd6a1606f4d1c
    BUG: 1221696
    Signed-off-by: Nithya Balachandran <nbalacha>
    Reviewed-on: http://review.gluster.org/10786
    Reviewed-by: Shyamsundar Ranganathan <srangana>
    Reviewed-by: Susant Palai <spalai>
    Tested-by: Gluster Build System <jenkins.com>