protocol/client: Prevent excessive logging of client's "disconnect" messages.

Problem: Currently when gluster volume start force is executed, client process
         will talk to glusterd to get the port of the brick. But if brick's path
         is not available it cannot return brick's port. So client process will
         keep connecting and disconnecting from glusterd for port-query which
         is ultimately responsible for execssive logging of disconnect messages.

Fix:     Message will be logged just once at INFO level after the first
         disconnect from glusterd. Afterwards "disconnect" messages will be
         logged in DEBUG mode.

Change-Id: I2b787f3820b5da45e090c562e5698fcfe24a02cd
BUG: 959969
Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
Reviewed-on: http://review.gluster.org/4953
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
doc: Move relevant files out of legacy.

Change-Id: Iff9166dd7baa3d60b70ffab5ce9a692d211fa4fb
BUG: 811311
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5091
Reviewed-by: Justin Clift <jclift@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
performance/write-behind: Enable write-behind when strict_O_DIRECT is not set.

When open() with O_DIRECT happens, write-behind was being disabled for the
fd irrespective of strict_O_DIRECT option. This commit disables write-behind
only when strict_O_DIRECT is enabled.

Change-Id: Ieef180e52910c3bf64d46b26b0e5dc3b8542f6d2
BUG: 923556
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/4697
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>