dht: make DHT xattr names configurable

This is necessary to support "DHT over DHT" configurations, so that the
upper and lower instances of DHT don't step all over each other.  Why
would we even consider such a thing?  Because it gives us the ability to
do data tiering and rack-aware placement, either by themselves or as
complements to other functionality such as erasure codes or
deduplication which save space but cost performance.  By setting up the
top-level DHT to place data into one of several lower-level DHT pools
based on policy instead of pure elastic hashing, we get better
performance for 90% of accesses and better storage efficiency for 90% of
data, all for relatively low effort.

Change-Id: I72e65c29edfc80babf39f7a2a00090f4588c4070
BUG: 924265
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/4694
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 25 insertions, 14 deletions

diff --git a/xlators/cluster/dht/src/dht-rebalance.c b/xlators/cluster/dht/src/dht-rebalance.c
index af31072aa..370118f98 100644
--- a/xlators/cluster/dht/src/dht-rebalance.c
+++ b/xlators/cluster/dht/src/dht-rebalance.c
@@ -102,12 +102,16 @@ gf_defrag_handle_hardlink (xlator_t *this, loc_t *loc, dict_t  *xattrs,
         data_t                 *data            = NULL;
         struct iatt             iatt            = {0,};
         int32_t                 op_errno        = 0;
+        dht_conf_t             *conf            = NULL;
 
         GF_VALIDATE_OR_GOTO ("defrag", loc, out);
         GF_VALIDATE_OR_GOTO ("defrag", loc->name, out);
         GF_VALIDATE_OR_GOTO ("defrag", stbuf, out);
         GF_VALIDATE_OR_GOTO ("defrag", this, out);
         GF_VALIDATE_OR_GOTO ("defrag", xattrs, out);
+        GF_VALIDATE_OR_GOTO ("defrag", this->private, out);
+
+        conf = this->private;
 
         if (uuid_is_null (loc->pargfid)) {
                 gf_log ("", GF_LOG_ERROR, "loc->pargfid is NULL for "
@@ -138,10 +142,10 @@ gf_defrag_handle_hardlink (xlator_t *this, loc_t *loc, dict_t  *xattrs,
         gf_log (this->name, GF_LOG_INFO, "Attempting to migrate hardlink %s "
                 "with gfid %s from %s -> %s", loc->name, uuid_utoa (loc->gfid),
                 cached_subvol->name, hashed_subvol->name);
-        data = dict_get (xattrs, DHT_LINKFILE_KEY);
+        data = dict_get (xattrs, conf->link_xattr_name);
         /* set linkto on cached -> hashed if not present, else link it */
         if (!data) {
-                ret = dict_set_str (xattrs, DHT_LINKFILE_KEY,
+                ret = dict_set_str (xattrs, conf->link_xattr_name,
                                     hashed_subvol->name);
                 if (ret) {
                         gf_log (this->name, GF_LOG_ERROR, "Failed to set "
@@ -241,12 +245,14 @@ static inline int
 __dht_rebalance_create_dst_file (xlator_t *to, xlator_t *from, loc_t *loc, struct iatt *stbuf,
                                  dict_t *dict, fd_t **dst_fd)
 {
-        xlator_t *this = NULL;
-        int       ret  = -1;
-        fd_t     *fd   = NULL;
-        struct iatt new_stbuf = {0,};
+        xlator_t    *this = NULL;
+        int          ret  = -1;
+        fd_t        *fd   = NULL;
+        struct iatt  new_stbuf = {0,};
+        dht_conf_t  *conf = NULL;
 
         this = THIS;
+        conf = this->private;
 
         ret = dict_set_static_bin (dict, "gfid-req", stbuf->ia_gfid, 16);
         if (ret) {
@@ -255,7 +261,7 @@ __dht_rebalance_create_dst_file (xlator_t *to, xlator_t *from, loc_t *loc, struc
                 goto out;
         }
 
-        ret = dict_set_str (dict, DHT_LINKFILE_KEY, from->name);
+        ret = dict_set_str (dict, conf->link_xattr_name, from->name);
         if (ret) {
                 gf_log (this->name, GF_LOG_ERROR,
                         "%s: failed to set gfid in dict for create", loc->path);
@@ -449,8 +455,10 @@ __dht_rebalance_open_src_file (xlator_t *from, xlator_t *to, loc_t *loc,
         dict_t      *dict = NULL;
         xlator_t    *this = NULL;
         struct iatt  iatt = {0,};
+        dht_conf_t  *conf = NULL;
 
         this = THIS;
+        conf = this->private;
 
         fd = fd_create (loc->inode, DHT_REBALANCE_PID);
         if (!fd) {
@@ -473,7 +481,7 @@ __dht_rebalance_open_src_file (xlator_t *from, xlator_t *to, loc_t *loc,
         if (!dict)
                 goto out;
 
-        ret = dict_set_str (dict, DHT_LINKFILE_KEY, to->name);
+        ret = dict_set_str (dict, conf->link_xattr_name, to->name);
         if (ret) {
                 gf_log (this->name, GF_LOG_ERROR,
                         "failed to set xattr in dict for %s (linkto:%s)",
@@ -526,12 +534,13 @@ migrate_special_files (xlator_t *this, xlator_t *from, xlator_t *to, loc_t *loc,
         dict_t      *dict     = NULL;
         char        *link     = NULL;
         struct iatt  stbuf    = {0,};
+        dht_conf_t  *conf     = this->private;
 
         dict = dict_new ();
         if (!dict)
                 goto out;
 
-        ret = dict_set_int32 (dict, DHT_LINKFILE_KEY, 256);
+        ret = dict_set_int32 (dict, conf->link_xattr_name, 256);
         if (ret) {
                 gf_log (this->name, GF_LOG_ERROR,
                         "%s: failed to set 'linkto' key in dict", loc->path);
@@ -547,12 +556,13 @@ migrate_special_files (xlator_t *this, xlator_t *from, xlator_t *to, loc_t *loc,
         }
 
         /* we no more require this key */
-        dict_del (dict, DHT_LINKFILE_KEY);
+        dict_del (dict, conf->link_xattr_name);
 
         /* file exists in target node, only if it is 'linkfile' its valid,
            otherwise, error out */
         if (!ret) {
-                if (!check_is_linkfile (loc->inode, &stbuf, rsp_dict)) {
+                if (!check_is_linkfile (loc->inode, &stbuf, rsp_dict,
+                                        conf->link_xattr_name)) {
                         gf_log (this->name, GF_LOG_WARNING,
                                 "%s: file exists in destination", loc->path);
                         ret = -1;
@@ -647,6 +657,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         dict_t         *xattr          = NULL;
         dict_t         *xattr_rsp      = NULL;
         int             file_has_holes = 0;
+        dht_conf_t     *conf           = this->private;
 
         gf_log (this->name, GF_LOG_INFO, "%s: attempting to move from %s to %s",
                 loc->path, from->name, to->name);
@@ -655,7 +666,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         if (!dict)
                 goto out;
 
-        ret = dict_set_int32 (dict, DHT_LINKFILE_KEY, 256);
+        ret = dict_set_int32 (dict, conf->link_xattr_name, 256);
         if (ret) {
                 gf_log (this->name, GF_LOG_ERROR,
                         "%s: failed to set 'linkto' key in dict", loc->path);
@@ -671,7 +682,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         }
 
         /* we no more require this key */
-        dict_del (dict, DHT_LINKFILE_KEY);
+        dict_del (dict, conf->link_xattr_name);
 
         /* preserve source mode, so set the same to the destination */
         src_ia_prot = stbuf.ia_prot;
@@ -842,7 +853,7 @@ dht_migrate_file (xlator_t *this, loc_t *loc, xlator_t *from, xlator_t *to,
         }
 
         /* remove the 'linkto' xattr from the destination */
-        ret = syncop_fremovexattr (to, dst_fd, DHT_LINKFILE_KEY);
+        ret = syncop_fremovexattr (to, dst_fd, conf->link_xattr_name);
         if (ret) {
                 gf_log (this->name, GF_LOG_WARNING,
                         "%s: failed to perform removexattr on %s (%s)",