afr: Take full locks in arbiter only for data transactions

Problem:
Sharding exposed a bug in arbiter config. where `dd` throughput was
extremely slow. Shard xlator was sending a fxattrop to update the file
size immediately after a writev. Arbiter was incorrectly over-riding the
LLONGMAX-1 start offset (for metadata domain locks) for this fxattrop,
causing the inodelk to be taken on the data domain. And since the
preceeding writev hadn't released the lock (afr does a 'lazy'
unlock if write succeeds on all bricks), this degraded to a blocking
lock causing extra lock/unlock calls and delays.

Fix:
Modify flock.l_len and flock.l_start to take full locks only for data
transactions.

> Reviewed-on: http://review.gluster.org/15641
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
(cherry picked from commit 3a97486d7f9d0db51abcb13dcd3bc9db935e3a60)

Change-Id: I906895da2f2d16813607e6c906cb4defb21d7c3b
BUG: 1375125
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reported-by: Max Raba <max.raba@comsysto.com>
Reviewed-on: http://review.gluster.org/15647
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>

0 files changed, 0 insertions, 0 deletions