cluster/dht: enable lookup-optimize by default

Lookup-optimize has been shown to improve create
performance. The code has been in the project for several
years and is considered stable.

Enabling this by default in order to test this in the
upstream regression runs.

Change-Id: Iab792979ee34f0af4713931e0b5b399c23f65313
updates: bz#1557435
BUG: 1557435
Signed-off-by: N Balachandran <nbalacha@redhat.com>

tests/features/unhashed-auto.t

@@ -114,7 +114,7 @@ TEST [ x"$new_hash" = x"00000001" ]
 
 # Unset the option and check that newly created directories get 1 in the
 # disk layout
-TEST $CLI volume reset $V0 cluster.lookup-optimize
+TEST $CLI volume set $V0 cluster.lookup-optimize off
 TEST mkdir $M0/dir1
 new_hash=$(get_xattr_hash $B0/${V0}1/dir1)
 TEST [ x"$new_hash" = x"00000001" ]

xlators/cluster/dht/src/dht-rebalance.c

@@ -4542,7 +4542,9 @@ gf_defrag_start_crawl (void *data)
 
         ret = syncop_setxattr (this, &loc, fix_layout, 0, NULL, NULL);
         if (ret) {
-                gf_log (this->name, GF_LOG_ERROR, "fix layout on %s failed",
+                gf_log (this->name, GF_LOG_ERROR,
+                        "Failed to set commit hash on %s. "
+                        "Rebalance cannot proceed.",
                         loc.path);
                 defrag->total_failures++;
                 ret = -1;

xlators/cluster/dht/src/dht-shared.c

@@ -976,7 +976,7 @@ struct volume_options options[] = {
         },
         { .key = {"lookup-optimize"},
           .type = GF_OPTION_TYPE_BOOL,
-          .default_value = "off",
+          .default_value = "on",
           .description = "This option if set to ON enables the optimization "
           "of -ve lookups, by not doing a lookup on non-hashed subvolumes for "
           "files, in case the hashed subvolume does not return any result. "