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: 1275173
Reviewed-on: http://review.gluster.org/12417
Signed-off-by: Saravanakumar Arumugam <sarumuga@redhat.com>
Reviewed-on: http://review.gluster.org/12428
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
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 428ed1d680b..f6bab2480ed 100644
--- a/xlators/features/changelog/src/changelog.c
+++ b/xlators/features/changelog/src/changelog.c
@@ -885,8 +885,24 @@ 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) {