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@redhat.com>
Reviewed-on: http://review.gluster.org/10786
Reviewed-by: Shyamsundar Ranganathan <srangana@redhat.com>
Reviewed-by: Susant Palai <spalai@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/xlators/cluster/dht/src/dht-rebalance.c b/xlators/cluster/dht/src/dht-rebalance.c
index 6ba9dd1e463..3ab73d4ef5b 100644
--- a/xlators/cluster/dht/src/dht-rebalance.c
+++ b/xlators/cluster/dht/src/dht-rebalance.c
@@ -2341,7 +2341,7 @@ gf_defrag_settle_hash (xlator_t *this, gf_defrag_info_t *defrag,
                        loc_t *loc, dict_t *fix_layout)
 {
         int     ret;
-
+        dht_conf_t *conf = NULL;
         /*
          * Now we're ready to update the directory commit hash for the volume
          * root, so that hash miscompares and broadcast lookups can stop.
@@ -2355,6 +2355,19 @@ gf_defrag_settle_hash (xlator_t *this, gf_defrag_info_t *defrag,
                 return 0;
         }
 
+        conf = this->private;
+        if (!conf) {
+                /*Uh oh
+                 */
+                return -1;
+        }
+
+        if (conf->local_subvols_cnt == 0) {
+                /* Commit hash updates are only done on local subvolumes
+                 */
+                return 0;
+        }
+
         ret = dict_set_uint32 (fix_layout, "new-commit-hash",
                                defrag->new_commit_hash);
         if (ret) {