afr,dht,ec: Replace GF_EVENT_CHILD_MODIFIED with event SOME_DESCENDENT_DOWN/UP

Backport of http://review.gluster.org/#/c/15764/

Currently these are few events related to child_up/down:
GF_EVENT_CHILD_UP :  Issued when any of the protocol client
connects.
GF_EVENT_CHILD_MODIFIED : Issued by afr/dht/ec
GF_EVENT_CHILD_DOWN : Issued when any of the protocol client
disconnects.
These events get modified at the dht/afr/ec layers. Here is a
brief on the same.

DHT:
- All the subvolumes reported once, and atleast one child came
  up, then GF_EVENT_CHILD_UP is issued
- connect GF_EVENT_CHILD_UP is issued
- disconnect GF_EVENT_CHILD_MODIFIED is issued
- All the subvolumes disconnected, GF_EVENT_CHILD_DOWN is issued

AFR:
- First subvolume came up, then GF_EVENT_CHILD_UP is issued
- Subsequent subvolumes coming up, results in GF_EVENT_CHILD_MODIFIED
- Any of the subvolumes go down, then GF_EVENT_SOME_CHILD_DOWN is issued
- Last up subvolume goes down, then GF_EVENT_CHILD_DOWN is issued

Until the patch [1] introduced GF_EVENT_SOME_CHILD_UP,
GF_EVENT_CHILD_MODIFIED was issued by afr/dht when any of the subvolumes
go up or down.

Now with md-cache changes, there is a necessity to differentiate between
child up and down. Hence, introducing GF_EVENT_SOME_DESCENDENT_DOWN/UP and
getting rid of GF_EVENT_CHILD_MODIFIED.

[1] http://review.gluster.org/12573

>Reviewed-on: http://review.gluster.org/15764
>CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
>NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
>Smoke: Gluster Build System <jenkins@build.gluster.org>
>Reviewed-by: N Balachandran <nbalacha@redhat.com>
>Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com> 
>Reviewed-by: Rajesh Joseph <rjoseph@redhat.com>
(cherry picked from commit f7ab6c45963fa0da68acedfb14281cd2456abc68)

Change-Id: I704140b6598f7ec705493251d2dbc4191c965a58
BUG: 1396880
Signed-off-by: Poornima G <pgurusid@redhat.com>
Reviewed-on: http://review.gluster.org/15890
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>

1 files changed, 16 insertions, 22 deletions

diff --git a/xlators/cluster/afr/src/afr-common.c b/xlators/cluster/afr/src/afr-common.c
index a406e43e9f1..e1ed4fc5b44 100644
--- a/xlators/cluster/afr/src/afr-common.c
+++ b/xlators/cluster/afr/src/afr-common.c
@@ -4570,27 +4570,21 @@ __afr_transform_event_from_state (afr_private_t *priv)
                 return GF_EVENT_MAXVAL;
 
         up_children = __afr_get_up_children_count (priv);
-        if (up_children) {
-                /* We received at least one child up and there are pending
-                 * notifications from some children. Treat these children as
-                 * having sent a GF_EVENT_CHILD_DOWN. i.e. set the event as
-                 * GF_EVENT_CHILD_MODIFIED, as done in afr_notify() */
-                for (i = 0; i < priv->child_count; i++) {
-                        if (priv->last_event[i])
-                                continue;
-                        priv->last_event[i] = GF_EVENT_CHILD_MODIFIED;
-                        priv->child_up[i] = 0;
-                }
+        /* Treat the children with pending notification, as having sent a
+         * GF_EVENT_CHILD_DOWN. i.e. set the event as GF_EVENT_SOME_DESCENDENT_DOWN,
+         * as done in afr_notify() */
+        for (i = 0; i < priv->child_count; i++) {
+                if (priv->last_event[i])
+                        continue;
+                priv->last_event[i] = GF_EVENT_SOME_DESCENDENT_DOWN;
+                priv->child_up[i] = 0;
+        }
+
+        if (up_children)
+                /* We received at least one child up */
                 return GF_EVENT_CHILD_UP;
-        } else {
-                for (i = 0; i < priv->child_count; i++) {
-                        if (priv->last_event[i])
-                                continue;
-                        priv->last_event[i] = GF_EVENT_SOME_CHILD_DOWN;
-                        priv->child_up[i] = 0;
-                }
+        else
                 return GF_EVENT_CHILD_DOWN;
-        }
 
         return GF_EVENT_MAXVAL;
 }
@@ -4759,7 +4753,7 @@ afr_notify (xlator_t *this, int32_t event,
                                           "subvol=%s", this->name);
 
                         } else {
-                                event = GF_EVENT_CHILD_MODIFIED;
+                                event = GF_EVENT_SOME_DESCENDENT_UP;
                         }
 
                         priv->last_event[idx] = event;
@@ -4783,7 +4777,7 @@ afr_notify (xlator_t *this, int32_t event,
                                 gf_event (EVENT_AFR_SUBVOLS_DOWN,
                                           "subvol=%s", this->name);
                         } else {
-                                event = GF_EVENT_SOME_CHILD_DOWN;
+                                event = GF_EVENT_SOME_DESCENDENT_DOWN;
                         }
 
                         priv->last_event[idx] = event;
@@ -4795,7 +4789,7 @@ afr_notify (xlator_t *this, int32_t event,
 
                         break;
 
-                case GF_EVENT_SOME_CHILD_DOWN:
+                case GF_EVENT_SOME_DESCENDENT_DOWN:
                         priv->last_event[idx] = event;
                         break;
                 case GF_EVENT_UPCALL: