features/changelog: record mknod if tier-dht linkto is set

This is a series of patches which aims to fix geo-replication
in a Tiering Volume.

Problem:
Consider, a file is placed in volume initially and then hot tier is
attached. During any operation on the file, due to lookup a linkto
file is created in hot tier.

Now, any namespace operation carried out on the file is recorded in
both cold and hot tier.
There is a room for races when both changelogs are replayed.

Solution:
So, We are going to replay (namespace related)operations
only in the hot tier.

Why?
a. If the file is directly placed in Hot tier, all fops will be
recorded in HOT tier.

b. If  the file is already present in Cold tier, and if any fop is
carried out, it creates linkto file in Hot tier.
Now, operations like UNLINK, RENAME are captured in Hot tier(by means of linkto file).

This way, we can get both tier's operation in HOT tier itself.

But, We may miss initial Data sync immediately after creating the
file as it is only recording MKNOD. So, if MKNOD encountered
with sticky bit set, queue DATA operation for the corresponding gfid.
( This geo-rep related changes are addressed in this patch: http://review.gluster.org/12326/ )

So, If tier-dht linkto is set, we need to record the corresponding
MKNOD. Earlier this was avoided as it was set as INTERNAL fop.
(This is addressed here in this patch)

Change-Id: I25514fe3e25f68592a8d6361507f8c8a4fcb70b1
BUG: 1266875
Signed-off-by: Saravanakumar Arumugam <sarumuga@redhat.com>
Reviewed-on: http://review.gluster.org/12417
Reviewed-by: Aravinda VK <avishwan@redhat.com>
Reviewed-by: Kotresh HR <khiremat@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Venky Shankar <vshankar@redhat.com>

1 files changed, 18 insertions, 2 deletions

diff --git a/xlators/features/changelog/src/changelog.c b/xlators/features/changelog/src/changelog.c
index 29e37a7ad56..08ef67dd65d 100644
--- a/xlators/features/changelog/src/changelog.c
+++ b/xlators/features/changelog/src/changelog.c
@@ -895,8 +895,24 @@ changelog_mknod (call_frame_t *frame,
         gf_boolean_t     barrier_enabled   = _gf_false;
 
         priv = this->private;
-        CHANGELOG_NOT_ACTIVE_THEN_GOTO (frame, priv, wind);
-        CHANGELOG_IF_INTERNAL_FOP_THEN_GOTO (frame, xdata, wind);
+
+        /* Check whether changelog active */
+        if (!(priv->active))
+                goto wind;
+
+        /* Check whether rebalance activity */
+        if (frame->root->pid == GF_CLIENT_PID_DEFRAG)
+                goto wind;
+
+        /* If tier-dht linkto is SET, ignore about verifiying :
+         * 1. Whether internal fop AND
+         * 2. Whether tier rebalance process activity (this will help in
+         * recording mknod if tier rebalance process calls this mknod) */
+        if (!(dict_get (xdata, "trusted.tier.tier-dht.linkto"))) {
+                CHANGELOG_IF_INTERNAL_FOP_THEN_GOTO (frame, xdata, wind);
+                if (frame->root->pid == GF_CLIENT_PID_TIER_DEFRAG)
+                        goto wind;
+        }
 
         ret = dict_get_ptr (xdata, "gfid-req", &uuid_req);
         if (ret) {