cluster/tier: add pause tier for snapshots

This is a backport of 12304

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>
Signed-off-by: Dan Lambright <dlambrig@redhat.com>

Conflicts:
	xlators/mgmt/glusterd/src/glusterd-messages.h

Change-Id: I5f039d8d38a4c915bd873969f336b96755a0b8f1
BUG: 1274101
Reviewed-on: http://review.gluster.org/12411
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Dan Lambright <dlambrig@redhat.com>
Tested-by: Dan Lambright <dlambrig@redhat.com>

1 files changed, 122 insertions, 3 deletions

diff --git a/xlators/cluster/dht/src/dht-rebalance.c b/xlators/cluster/dht/src/dht-rebalance.c
index 1e98142e9ec..3cb247f1865 100644
--- a/xlators/cluster/dht/src/dht-rebalance.c
+++ b/xlators/cluster/dht/src/dht-rebalance.c
@@ -731,7 +731,7 @@ out:
 
 static inline int
 __dht_rebalance_migrate_data (xlator_t *from, xlator_t *to, fd_t *src, fd_t *dst,
-                             uint64_t ia_size, int hole_exists)
+                              uint64_t ia_size, int hole_exists)
 {
         int            ret    = 0;
         int            count  = 0;
@@ -783,6 +783,68 @@ __dht_rebalance_migrate_data (xlator_t *from, xlator_t *to, fd_t *src, fd_t *dst
         return ret;
 }
 
+static int
+__tier_migrate_data (gf_defrag_info_t *defrag, xlator_t *from, xlator_t *to, fd_t *src, fd_t *dst,
+                     uint64_t ia_size, int hole_exists)
+{
+        int            ret    = 0;
+        int            count  = 0;
+        off_t          offset = 0;
+        struct iovec  *vector = NULL;
+        struct iobref *iobref = NULL;
+        uint64_t       total  = 0;
+        size_t         read_size = 0;
+
+        /* if file size is '0', no need to enter this loop */
+        while (total < ia_size) {
+
+                read_size = (((ia_size - total) > DHT_REBALANCE_BLKSIZE) ?
+                             DHT_REBALANCE_BLKSIZE : (ia_size - total));
+
+                ret = syncop_readv (from, src, read_size,
+                                    offset, 0, &vector, &count, &iobref, NULL,
+                                    NULL);
+                if (!ret || (ret < 0)) {
+                        break;
+                }
+
+                if (hole_exists)
+                        ret = dht_write_with_holes (to, dst, vector, count,
+                                                    ret, offset, iobref);
+                else
+                        ret = syncop_writev (to, dst, vector, count,
+                                             offset, iobref, 0, NULL, NULL);
+                if (defrag->tier_conf.request_pause) {
+                        gf_msg ("tier", GF_LOG_INFO, 0,
+                                DHT_MSG_TIER_PAUSED,
+                                "Migrate file paused");
+                        ret = -1;
+                }
+
+                if (ret < 0) {
+                        break;
+                }
+                offset += ret;
+                total += ret;
+
+                GF_FREE (vector);
+                if (iobref)
+                        iobref_unref (iobref);
+                iobref = NULL;
+                vector = NULL;
+        }
+        if (iobref)
+                iobref_unref (iobref);
+        GF_FREE (vector);
+
+        if (ret >= 0)
+                ret = 0;
+        else
+                ret = -1;
+
+        return ret;
+}
+
 
 static inline int
 __dht_rebalance_open_src_file (xlator_t *from, xlator_t *to, loc_t *loc,
@@ -1255,8 +1317,14 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
 
 
         /* All I/O happens in this function */
-        ret = __dht_rebalance_migrate_data (from, to, src_fd, dst_fd,
-					    stbuf.ia_size, file_has_holes);
+        if (defrag->cmd == GF_DEFRAG_CMD_START_TIER) {
+                ret = __tier_migrate_data (defrag, from, to, src_fd, dst_fd,
+                                                    stbuf.ia_size, file_has_holes);
+        } else {
+                ret = __dht_rebalance_migrate_data (from, to, src_fd, dst_fd,
+                                                    stbuf.ia_size, file_has_holes);
+        }
+
         if (ret) {
                 gf_msg (this->name, GF_LOG_ERROR, 0,
                         DHT_MSG_MIGRATE_FILE_FAILED,
@@ -3420,6 +3488,57 @@ out:
 }
 
 int
+gf_defrag_pause_tier (xlator_t *this, gf_defrag_info_t *defrag)
+{
+        int          poll           = 0;
+        int          ret            = 0;
+        int          usec_sleep     = 100000;  /* 1/10th of a sec */
+        int          poll_max       = 15;      /* 15 times = wait at most 3/2 sec */
+
+        if (defrag->defrag_status != GF_DEFRAG_STATUS_STARTED)
+                goto out;
+
+        /*
+         * Set flag requesting to pause tiering. Wait a finite time for
+         * tiering to actually stop as indicated by the "paused" boolean,
+         * before returning success or failure.
+         */
+        defrag->tier_conf.request_pause = 1;
+
+        for (poll = 0; poll < poll_max; poll++) {
+                if ((defrag->tier_conf.paused == _gf_true) ||
+                    (defrag->defrag_status != GF_DEFRAG_STATUS_STARTED)) {
+                        goto out;
+                }
+
+                usleep (usec_sleep);
+        }
+
+        ret = -1;
+
+out:
+
+        gf_msg (this->name, GF_LOG_DEBUG, 0,
+                DHT_MSG_TIER_PAUSED,
+                "Pause tiering ret=%d", ret);
+
+        return ret;
+}
+
+int
+gf_defrag_resume_tier (xlator_t *this, gf_defrag_info_t *defrag)
+{
+        gf_msg (this->name, GF_LOG_DEBUG, 0,
+                DHT_MSG_TIER_RESUME,
+                "Resume tiering");
+
+        defrag->tier_conf.request_pause = 0;
+        defrag->tier_conf.paused = _gf_false;
+
+        return 0;
+}
+
+int
 gf_defrag_start_detach_tier (gf_defrag_info_t *defrag)
 {
         defrag->cmd = GF_DEFRAG_CMD_START_DETACH_TIER;