afr: arbiter xlator

This patch adds the arbiter translator into the tree. This is a server
side xlator used for replica 3 volumes. It sits above posix and will be
loaded on the 3rd (last) brick of every afr subvolume in a replica 3
configuration. It intercepts inode read/write operations: reads are
unwound with ENOTCONN, inode writes are unwound with success without
actually passing them down to posix. Metadata operations are allowed to
pass through.

The CLI for creating a 3 way replica with arbiter is also added but kept
disabled (A 'normal' 3 way replica is created instead).

This patch is a part of the arbiter logic implementation for 3 way AFR,
details of which can be found at http://review.gluster.org/#/c/9656/

Change-Id: I395b81f49d5da52c466daf5c8518f1bbad9c16fa
BUG: 1199985
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/9840
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/xlators/mgmt/glusterd/src/glusterd-volgen.c b/xlators/mgmt/glusterd/src/glusterd-volgen.c
index 79da432bafe..6f6d1095edb 100644
--- a/xlators/mgmt/glusterd/src/glusterd-volgen.c
+++ b/xlators/mgmt/glusterd/src/glusterd-volgen.c
@@ -1496,6 +1496,25 @@ out:
 }
 
 static int
+brick_graph_add_arbiter (volgen_graph_t *graph, glusterd_volinfo_t *volinfo,
+                         dict_t *set_dict, glusterd_brickinfo_t *brickinfo)
+{
+        xlator_t *xl = NULL;
+        int ret = -1;
+
+        if (volinfo->arbiter_count != 1)
+                return 0;
+        /*TODO: Parse brickinfo and add the arbiter xlator only if brick is the
+         * last brick (i.e. 3rd brick) of the replcia pair.*/
+        xl = volgen_graph_add (graph, "features/arbiter", volinfo->volname);
+        if (!xl)
+                goto out;
+        ret = 0;
+out:
+        return ret;
+}
+
+static int
 brick_graph_add_bd (volgen_graph_t *graph, glusterd_volinfo_t *volinfo,
                      dict_t *set_dict, glusterd_brickinfo_t *brickinfo)
 {
@@ -2140,6 +2159,7 @@ static volgen_brick_xlator_t server_graph_table[] = {
         {brick_graph_add_changetimerecorder, "changetimerecorder"},
         {brick_graph_add_bd, "bd"},
         {brick_graph_add_trash, "trash"},
+        {brick_graph_add_arbiter, "arbiter"},
         {brick_graph_add_posix, "posix"},
 };