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, 11 insertions, 6 deletions

diff --git a/xlators/cluster/dht/src/dht-common.h b/xlators/cluster/dht/src/dht-common.h
index 65983c0c49f..3679918d79f 100644
--- a/xlators/cluster/dht/src/dht-common.h
+++ b/xlators/cluster/dht/src/dht-common.h
@@ -290,6 +290,11 @@ struct dht_conf {
         gf_boolean_t    rsync_regex_valid;
         regex_t         extra_regex;
         gf_boolean_t    extra_regex_valid;
+
+        /* Support variable xattr names. */
+        char            *xattr_name;
+        char            *link_xattr_name;
+        char            *wild_xattr_name;
 };
 typedef struct dht_conf dht_conf_t;
 
@@ -320,13 +325,12 @@ typedef enum {
 #define DHT_MIGRATION_IN_PROGRESS 1
 #define DHT_MIGRATION_COMPLETED   2
 
-#define DHT_LINKFILE_KEY         "trusted.glusterfs.dht.linkto"
 #define DHT_LINKFILE_MODE        (S_ISVTX)
 
-#define check_is_linkfile(i,s,x) (                                      \
+#define check_is_linkfile(i,s,x,n) (                                      \
                 ((st_mode_from_ia ((s)->ia_prot, (s)->ia_type) & ~S_IFMT) \
-                 == DHT_LINKFILE_MODE) &&                               \
-                dict_get (x, DHT_LINKFILE_KEY))
+                 == DHT_LINKFILE_MODE) &&                                 \
+                dict_get (x, n))
 
 #define IS_DHT_MIGRATION_PHASE2(buf)  (                                 \
                 IA_ISREG ((buf)->ia_type) &&                            \
@@ -438,7 +442,8 @@ int       dht_subvol_cnt (xlator_t *this, xlator_t *subvol);
 int dht_hash_compute (xlator_t *this, int type, const char *name, uint32_t *hash_p);
 
 int dht_linkfile_create (call_frame_t    *frame, fop_mknod_cbk_t linkfile_cbk,
-                         xlator_t        *tovol, xlator_t *fromvol, loc_t *loc);
+                         xlator_t        *this, xlator_t *tovol,
+                         xlator_t        *fromvol, loc_t *loc);
 int                                       dht_lookup_directory (call_frame_t *frame, xlator_t *this, loc_t *loc);
 int                                       dht_lookup_everywhere (call_frame_t *frame, xlator_t *this, loc_t *loc);
 int
@@ -740,7 +745,7 @@ dht_dir_attr_heal (void *data);
 int
 dht_dir_attr_heal_done (int ret, call_frame_t *sync_frame, void *data);
 int
-dht_dir_has_layout (dict_t *xattr);
+dht_dir_has_layout (dict_t *xattr, char *name);
 gf_boolean_t
 dht_is_subvol_in_layout (dht_layout_t *layout, xlator_t *xlator);
 xlator_t *