cluster/ec: Implement gfid-hash read-policy

Add a policy in ec to performs reads from same bricks as long as they
are good. Based on the gfid of the file/directory it determines the
bricks to be considered for reading.

Change-Id: Ic97b5c54c086a28b5e07a330a4fd448551b49376
BUG: 1261260
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/12133
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Xavier Hernandez <xhernandez@datalab.es>

3 files changed, 73 insertions, 10 deletions

diff --git a/xlators/cluster/ec/src/ec-common.c b/xlators/cluster/ec/src/ec-common.c
index d0c9f97ab28..39a529d3a0b 100644
--- a/xlators/cluster/ec/src/ec-common.c
+++ b/xlators/cluster/ec/src/ec-common.c
@@ -9,6 +9,7 @@
 */
 
 #include "byte-order.h"
+#include "hashfn.h"
 
 #include "ec-mem-types.h"
 #include "ec-data.h"
@@ -20,6 +21,25 @@
 #include "ec.h"
 #include "ec-messages.h"
 
+uint32_t
+ec_select_first_by_read_policy (ec_t *ec, ec_fop_data_t *fop)
+{
+        if (ec->read_policy == EC_ROUND_ROBIN) {
+                return ec->idx;
+        } else if (ec->read_policy == EC_GFID_HASH) {
+                if (fop->use_fd) {
+                        return SuperFastHash((char *)fop->fd->inode->gfid,
+                                   sizeof(fop->fd->inode->gfid)) % ec->nodes;
+                } else {
+                        if (gf_uuid_is_null (fop->loc[0].gfid))
+                                loc_gfid (&fop->loc[0], fop->loc[0].gfid);
+                        return SuperFastHash((char *)fop->loc[0].gfid,
+                                   sizeof(fop->loc[0].gfid)) % ec->nodes;
+                }
+        }
+        return 0;
+}
+
 int32_t ec_child_valid(ec_t * ec, ec_fop_data_t * fop, int32_t idx)
 {
     return (idx < ec->nodes) && (((fop->remaining >> idx) & 1) == 1);
@@ -415,12 +435,13 @@ int32_t ec_child_select(ec_fop_data_t * fop)
             fop->minimum = 1;
     }
 
-    first = ec->idx;
-    if (++first >= ec->nodes)
-    {
-        first = 0;
+    if (ec->read_policy == EC_ROUND_ROBIN) {
+            first = ec->idx;
+            if (++first >= ec->nodes) {
+                first = 0;
+            }
+            ec->idx = first;
     }
-    ec->idx = first;
 
     /*Unconditionally wind on healing subvolumes*/
     fop->mask |= fop->healing;
@@ -518,14 +539,12 @@ void ec_dispatch_start(ec_fop_data_t * fop)
 
 void ec_dispatch_one(ec_fop_data_t * fop)
 {
-    ec_t * ec = fop->xl->private;
-
     ec_dispatch_start(fop);
 
     if (ec_child_select(fop))
     {
         fop->expected = 1;
-        fop->first = ec->idx;
+        fop->first = ec_select_first_by_read_policy (fop->xl->private, fop);
 
         ec_dispatch_next(fop, fop->first);
     }
@@ -589,7 +608,7 @@ void ec_dispatch_min(ec_fop_data_t * fop)
     if (ec_child_select(fop))
     {
         fop->expected = count = ec->fragments;
-        fop->first = ec->idx;
+        fop->first = ec_select_first_by_read_policy (fop->xl->private, fop);
         idx = fop->first - 1;
         mask = 0;
         while (count-- > 0)
diff --git a/xlators/cluster/ec/src/ec.c b/xlators/cluster/ec/src/ec.c
index 11c71743458..06f814f9f5c 100644
--- a/xlators/cluster/ec/src/ec.c
+++ b/xlators/cluster/ec/src/ec.c
@@ -21,6 +21,11 @@
 #include "ec-messages.h"
 #include "ec-heald.h"
 
+static char *ec_read_policies[EC_READ_POLICY_MAX + 1] = {
+        [EC_ROUND_ROBIN] = "round-robin",
+        [EC_GFID_HASH] = "gfid-hash",
+        [EC_READ_POLICY_MAX] = NULL
+};
 #define EC_MAX_FRAGMENTS EC_METHOD_MAX_FRAGMENTS
 /* The maximum number of nodes is derived from the maximum allowed fragments
  * using the rule that redundancy cannot be equal or greater than the number
@@ -231,10 +236,24 @@ ec_configure_background_heal_opts (ec_t *ec, int background_heals,
         ec->background_heals = background_heals;
 }
 
+int
+ec_assign_read_policy (ec_t *ec, char *read_policy)
+{
+        int read_policy_idx = -1;
+
+        read_policy_idx = gf_get_index_by_elem (ec_read_policies, read_policy);
+        if (read_policy_idx < 0 || read_policy_idx >= EC_READ_POLICY_MAX)
+                return -1;
+
+        ec->read_policy = read_policy_idx;
+        return 0;
+}
+
 int32_t
 reconfigure (xlator_t *this, dict_t *options)
 {
         ec_t     *ec              = this->private;
+        char     *read_policy     = NULL;
         uint32_t heal_wait_qlen   = 0;
         uint32_t background_heals = 0;
 
@@ -250,6 +269,10 @@ reconfigure (xlator_t *this, dict_t *options)
                           int32, failed);
         ec_configure_background_heal_opts (ec, background_heals,
                                            heal_wait_qlen);
+        GF_OPTION_RECONF ("read-policy", read_policy, options, str, failed);
+        if (ec_assign_read_policy (ec, read_policy))
+                goto failed;
+
         return 0;
 failed:
         return -1;
@@ -514,7 +537,8 @@ notify (xlator_t *this, int32_t event, void *data, ...)
 int32_t
 init (xlator_t *this)
 {
-    ec_t *ec = NULL;
+    ec_t *ec          = NULL;
+    char *read_policy = NULL;
 
     if (this->parents == NULL)
     {
@@ -576,6 +600,9 @@ init (xlator_t *this)
     GF_OPTION_INIT ("heal-wait-qlength", ec->heal_wait_qlen, uint32, failed);
     ec_configure_background_heal_opts (ec, ec->background_heals,
                                        ec->heal_wait_qlen);
+    GF_OPTION_INIT ("read-policy", read_policy, str, failed);
+    if (ec_assign_read_policy (ec, read_policy))
+            goto failed;
 
     if (ec->shd.iamshd)
             ec_selfheal_daemon_init (this);
@@ -1191,6 +1218,7 @@ int32_t ec_dump_private(xlator_t *this)
     gf_proc_dump_write("heal-wait-qlength", "%d", ec->heal_wait_qlen);
     gf_proc_dump_write("healers", "%d", ec->healers);
     gf_proc_dump_write("heal-waiters", "%d", ec->heal_waiters);
+    gf_proc_dump_write("read-policy", "%s", ec_read_policies[ec->read_policy]);
 
     return 0;
 }
@@ -1298,5 +1326,14 @@ struct volume_options options[] =
       .description = "time interval for checking the need to self-heal "
                      "in self-heal-daemon"
     },
+    { .key = {"read-policy" },
+      .type = GF_OPTION_TYPE_STR,
+      .value = {"round-robin", "gfid-hash"},
+      .default_value = "round-robin",
+      .description = "inode-read fops happen only on 'k' number of bricks in"
+              " n=k+m disperse subvolume. 'round-robin' selects the read"
+              " subvolume using round-robin algo. 'gfid-hash' selects read"
+              " subvolume based on hash of the gfid of that file/directory.",
+    },
     { }
 };
diff --git a/xlators/cluster/ec/src/ec.h b/xlators/cluster/ec/src/ec.h
index f335fd52afc..4ee7983b289 100644
--- a/xlators/cluster/ec/src/ec.h
+++ b/xlators/cluster/ec/src/ec.h
@@ -25,6 +25,12 @@
 
 #define EC_VERSION_SIZE 2
 
+typedef enum {
+        EC_ROUND_ROBIN,
+        EC_GFID_HASH,
+        EC_READ_POLICY_MAX
+} ec_read_policy_t;
+
 struct _ec
 {
     xlator_t *        xl;
@@ -58,6 +64,7 @@ struct _ec
     ec_self_heald_t   shd;
     char              vol_uuid[UUID_SIZE + 1];
     dict_t           *leaf_to_subvolid;
+    ec_read_policy_t  read_policy;
 };
 
 void ec_pending_fops_completed(ec_t *ec);