cluster/tier: add pause tier for snapshots

Snaps of tiered volumes cannot handle files undergoing migration.
We implement a helper mechanism to "pause" migration. Any files
undergoing migration are aborted. Clean up is done to remove
sticky bits and data at the destination. Migration is restarted
after snap completes.

For testing an internal switch is added. It is not exposed externally.

gluster volume set vol1 tier-pause [true|false]

Change-Id: Ia85bbf89ac142e9b7e73fcbef98bb9da86097799
BUG: 1267950
Signed-off-by: Dan Lambright <dlambrig@redhat.com>
Reviewed-on: http://review.gluster.org/12304
Reviewed-by: N Balachandran <nbalacha@redhat.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 67 insertions, 1 deletions

diff --git a/xlators/cluster/dht/src/tier.c b/xlators/cluster/dht/src/tier.c
index d85fe41dcb0..9dcbc760330 100644
--- a/xlators/cluster/dht/src/tier.c
+++ b/xlators/cluster/dht/src/tier.c
@@ -307,6 +307,13 @@ tier_migrate_using_query_file (void *_args)
                 per_file_status      = 0;
                 per_link_status      = 0;
 
+                if (defrag->tier_conf.request_pause) {
+                        gf_msg (this->name, GF_LOG_INFO, 0,
+                                DHT_MSG_LOG_TIER_STATUS,
+                                "Tiering paused. Exiting tier_migrate_using_query_file");
+                        break;
+                }
+
                 memset (gfid_str, 0, UUID_CANONICAL_FORM_LEN+1);
                 memset (query_record->_link_info_str, 0, DB_QUERY_RECORD_SIZE);
 
@@ -368,6 +375,14 @@ tier_migrate_using_query_file (void *_args)
                 /* Per link of file */
                 while (token_str != NULL) {
 
+                        if (defrag->tier_conf.request_pause) {
+                                gf_msg (this->name, GF_LOG_INFO, 0,
+                                        DHT_MSG_LOG_TIER_STATUS,
+                                        "Tiering paused. "
+                                        "Exiting tier_migrate_using_query_file");
+                                goto abort;
+                        }
+
                         link_str = gf_strdup (token_str);
 
                         if (!link_info) {
@@ -485,6 +500,14 @@ tier_migrate_using_query_file (void *_args)
 
                         gf_uuid_copy (loc.gfid, loc.inode->gfid);
 
+                        if (defrag->tier_conf.request_pause) {
+                                gf_msg (this->name, GF_LOG_INFO, 0,
+                                        DHT_MSG_LOG_TIER_STATUS,
+                                        "Tiering paused. "
+                                        "Exiting tier_migrate_using_query_file");
+                                goto abort;
+                        }
+
                         ret = syncop_setxattr (this, &loc, migrate_data, 0,
                                                NULL, NULL);
                         if (ret) {
@@ -1347,6 +1370,11 @@ tier_start (xlator_t *this, gf_defrag_info_t *defrag)
                         goto out;
                 }
 
+                if (defrag->tier_conf.request_pause)
+                        defrag->tier_conf.paused = _gf_true;
+                else
+                        defrag->tier_conf.paused = _gf_false;
+
                 sleep(1);
 
                 if (defrag->defrag_status != GF_DEFRAG_STATUS_STARTED) {
@@ -1368,6 +1396,11 @@ tier_start (xlator_t *this, gf_defrag_info_t *defrag)
                         goto out;
                 }
 
+                if ((defrag->tier_conf.paused) ||
+                    (defrag->tier_conf.request_pause))
+                        continue;
+
+
                 /* To have proper synchronization amongst all
                  * brick holding nodes, so that promotion and demotions
                  * start atomicly w.r.t promotion/demotion frequency
@@ -1658,6 +1691,7 @@ tier_init (xlator_t *this)
         gf_defrag_info_t *defrag         = NULL;
         char             *voldir         = NULL;
         char             *mode           = NULL;
+        char             *paused         = NULL;
 
         ret = dht_init (this);
         if (ret) {
@@ -1776,7 +1810,15 @@ tier_init (xlator_t *this)
                 defrag->tier_conf.mode = ret;
         }
 
-        ret = gf_asprintf (&voldir, "%s/%s",
+        defrag->tier_conf.request_pause = 0;
+
+        ret = dict_get_str (this->options,
+                              "tier-pause", &paused);
+
+        if (paused && strcmp (paused, "on") == 0)
+                defrag->tier_conf.request_pause = 1;
+
+        ret = gf_asprintf(&voldir, "%s/%s",
                           DEFAULT_VAR_RUN_DIRECTORY,
                           this->name);
         if (ret < 0)
@@ -1844,6 +1886,9 @@ tier_reconfigure (xlator_t *this, dict_t *options)
         gf_defrag_info_t *defrag         = NULL;
         char             *mode           = NULL;
         int               migrate_mb     = 0;
+        gf_boolean_t      req_pause      = _gf_false;
+        int               ret            = 0;
+
         conf = this->private;
 
         if (conf->defrag) {
@@ -1885,6 +1930,27 @@ tier_reconfigure (xlator_t *this, dict_t *options)
                 GF_OPTION_RECONF ("tier-max-files",
                                   defrag->tier_conf.max_migrate_files, options,
                                   int32, out);
+
+                GF_OPTION_RECONF ("tier-pause",
+                                  req_pause, options,
+                                  bool, out);
+
+                if (req_pause == _gf_true) {
+                        ret = gf_defrag_pause_tier (this, defrag);
+                        if (ret) {
+                                gf_msg (this->name, GF_LOG_ERROR, 0,
+                                        DHT_MSG_LOG_TIER_ERROR,
+                                        "pause tier failed on reconfigure");
+                        }
+                } else {
+                        ret = gf_defrag_resume_tier (this, defrag);
+                        if (ret) {
+                                gf_msg (this->name, GF_LOG_ERROR, 0,
+                                        DHT_MSG_LOG_TIER_ERROR,
+                                        "resume tier failed on reconfigure");
+                        }
+                }
+
         }
 
 out: