dht: make lookup-unhashed=auto do something actually useful

The key concept here is to determine whether a directory is "clean" by
comparing its last-known-good topology to the current one for the
volume.  These are stored as "commit hashes" on the directory and the
volume root respectively.  The volume's commit hash changes whenever a
brick is added or removed, and a fix-layout is done.  A directory's
commit hash changes only when a full rebalance (not just fix-layout)
is done on it.  If all bricks are present and have a directory
commit hash that matches the volume commit hash, then we can assume
that every file is in its "proper" place. Therefore, if we look for
a file in that proper place and don't find it, we can assume it's not
on any other subvolume and *safely* skip the global (broadcast to all)
lookup.

Change-Id: Id6ce4593ba1f7daffa74cfab591cb45960629ae3
BUG: 1220064
Reviewed-on-master: http://review.gluster.org/#/c/7702/
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Signed-off-by: Shyam <srangana@redhat.com>
Reviewed-on: http://review.gluster.org/10729
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/xlators/cluster/dht/src/dht-shared.c b/xlators/cluster/dht/src/dht-shared.c
index ffabc820d70..a1f72a85112 100644
--- a/xlators/cluster/dht/src/dht-shared.c
+++ b/xlators/cluster/dht/src/dht-shared.c
@@ -569,6 +569,7 @@ dht_init (xlator_t *this)
         int                              cmd            = 0;
         char                            *node_uuid      = NULL;
         int                              throttle_count = 0;
+        uint32_t                         commit_hash    = 0;
 
         GF_VALIDATE_OR_GOTO ("dht", this, err);
 
@@ -590,6 +591,15 @@ dht_init (xlator_t *this)
                 goto err;
         }
 
+        /* We get the commit-hash to set only for rebalance process */
+        if (dict_get_uint32 (this->options,
+                             "commit-hash", &commit_hash) == 0) {
+                gf_log (this->name, GF_LOG_INFO, "%s using commit hash %u",
+                        __func__, commit_hash);
+                conf->vol_commit_hash = commit_hash;
+                conf->vch_forced = _gf_true;
+        }
+
         ret = dict_get_int32 (this->options, "rebalance-cmd", &cmd);
 
         if (cmd) {
@@ -760,6 +770,8 @@ dht_init (xlator_t *this)
         GF_OPTION_INIT ("xattr-name", conf->xattr_name, str, err);
         gf_asprintf (&conf->link_xattr_name, "%s."DHT_LINKFILE_STR,
                      conf->xattr_name);
+        gf_asprintf (&conf->commithash_xattr_name, "%s."DHT_COMMITHASH_STR,
+                     conf->xattr_name);
         gf_asprintf (&conf->wild_xattr_name, "%s*", conf->xattr_name);
         if (!conf->link_xattr_name || !conf->wild_xattr_name) {
                 goto err;
@@ -871,6 +883,9 @@ struct volume_options options[] = {
         { .key  = {"rebalance-cmd"},
           .type = GF_OPTION_TYPE_INT,
         },
+        { .key = {"commit-hash"},
+          .type = GF_OPTION_TYPE_INT,
+        },
         { .key = {"node-uuid"},
           .type = GF_OPTION_TYPE_STR,
         },