features/changelog : Improvement in changelog "encoding-change".

change in encoding method of changelog was critical section for
"fop dispatch thread", "roll-over thread" and "reconfigure dispatch thread".

In this patch the "encoding-method" is changed by the reconfigure dispatch thread
lazily during handle_change, which solves the concurrency among the racing
threads.

BUG: 1002940
Change-Id: I78c3e8887efa46d0fcc60755cdf4243031cfa3eb
Signed-off-by: Ajeet Jha <ajha@redhat.com>
Reviewed-on: http://review.gluster.org/5844
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Harshavardhana <harsha@harshavardhana.net>

4 files changed, 26 insertions, 17 deletions

diff --git a/xlators/features/changelog/src/changelog-encoders.c b/xlators/features/changelog/src/changelog-encoders.c
index c71ea9270b0..553eec85c30 100644
--- a/xlators/features/changelog/src/changelog-encoders.c
+++ b/xlators/features/changelog/src/changelog-encoders.c
@@ -154,3 +154,23 @@ changelog_encode_binary (xlator_t *this, changelog_log_data_t *cld)
 
         return changelog_write_change (priv, buffer, off);
 }
+
+static struct changelog_encoder
+cb_encoder[] = {
+        [CHANGELOG_ENCODE_BINARY] =
+        {
+                .encoder = CHANGELOG_ENCODE_BINARY,
+                .encode = changelog_encode_binary,
+        },
+        [CHANGELOG_ENCODE_ASCII] =
+        {
+                .encoder = CHANGELOG_ENCODE_ASCII,
+                .encode = changelog_encode_ascii,
+        },
+};
+
+void
+changelog_encode_change( changelog_priv_t * priv)
+{
+        priv->ce = &cb_encoder[priv->encode_mode];
+}
diff --git a/xlators/features/changelog/src/changelog-encoders.h b/xlators/features/changelog/src/changelog-encoders.h
index 43deb1307d7..a3efbee05ee 100644
--- a/xlators/features/changelog/src/changelog-encoders.h
+++ b/xlators/features/changelog/src/changelog-encoders.h
@@ -40,5 +40,7 @@ int
 changelog_encode_binary (xlator_t *, changelog_log_data_t *);
 int
 changelog_encode_ascii (xlator_t *, changelog_log_data_t *);
+void
+changelog_encode_change(changelog_priv_t *);
 
 #endif /* _CHANGELOG_ENCODERS_H */
diff --git a/xlators/features/changelog/src/changelog-helpers.c b/xlators/features/changelog/src/changelog-helpers.c
index c1bb6e5fef9..7ab0091b592 100644
--- a/xlators/features/changelog/src/changelog-helpers.c
+++ b/xlators/features/changelog/src/changelog-helpers.c
@@ -21,6 +21,7 @@
 #include "changelog-helpers.h"
 #include "changelog-mem-types.h"
 
+#include "changelog-encoders.h"
 #include <pthread.h>
 
 void
@@ -201,7 +202,7 @@ changelog_open (xlator_t *this,
         (void) snprintf (buffer, 1024, CHANGELOG_HEADER,
                          CHANGELOG_VERSION_MAJOR,
                          CHANGELOG_VERSION_MINOR,
-                         priv->encode_mode);
+                         priv->ce->encoder);
         ret = changelog_write_change (priv, buffer, strlen (buffer));
         if (ret) {
                 close (priv->changelog_fd);
@@ -267,6 +268,7 @@ changelog_handle_change (xlator_t *this,
         int ret = 0;
 
         if (CHANGELOG_TYPE_IS_ROLLOVER (cld->cld_type)) {
+                changelog_encode_change(priv);
                 ret = changelog_start_next_change (this, priv,
                                                    cld->cld_roll_time,
                                                    cld->cld_finale);
diff --git a/xlators/features/changelog/src/changelog.c b/xlators/features/changelog/src/changelog.c
index 0a70fa0c760..cea0e8c70b5 100644
--- a/xlators/features/changelog/src/changelog.c
+++ b/xlators/features/changelog/src/changelog.c
@@ -36,20 +36,6 @@ cb_bootstrap[] = {
         },
 };
 
-static struct changelog_encoder
-cb_encoder[] = {
-        [CHANGELOG_ENCODE_BINARY] =
-        {
-                .encoder = CHANGELOG_ENCODE_BINARY,
-                .encode = changelog_encode_binary,
-        },
-        [CHANGELOG_ENCODE_ASCII] =
-        {
-                .encoder = CHANGELOG_ENCODE_ASCII,
-                .encode = changelog_encode_ascii,
-        },
-};
-
 /* Entry operations - TYPE III */
 
 /**
@@ -1363,8 +1349,7 @@ init (xlator_t *this)
 
         GF_OPTION_INIT ("fsync-interval", priv->fsync_interval, int32, out);
 
-        GF_ASSERT (cb_encoder[priv->encode_mode].encoder == priv->encode_mode);
-        priv->ce = &cb_encoder[priv->encode_mode];
+        changelog_encode_change(priv);
 
         GF_ASSERT (cb_bootstrap[priv->op_mode].mode == priv->op_mode);
         priv->cb = &cb_bootstrap[priv->op_mode];