libglusterfs: fix race condition in client_ctx_set

	follow procedures:
	1.thread1 client_ctx_get return NULL
	2.thread 2 client_ctx_set ctx1 ok
	3.thread1 client_ctx_set ctx2 ok

	thread1 use ctx1, thread2 use ctx2 and ctx1 will leak

Change-Id: I990b02905edd1b3179323ada56888f852d20f538
BUG: 1449232
Signed-off-by: Zhou Zhengping <johnzzpcrystal@gmail.com>
Reviewed-on: https://review.gluster.org/17219
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Jeff Darcy <jeff@pl.atyp.us>

2 files changed, 44 insertions, 34 deletions

diff --git a/libglusterfs/src/client_t.c b/libglusterfs/src/client_t.c
index 1adfef5c7e3..62cfbc422f8 100644
--- a/libglusterfs/src/client_t.c
+++ b/libglusterfs/src/client_t.c
@@ -439,7 +439,31 @@ gf_client_unref (client_t *client)
 
 
 static int
-client_ctx_set_int (client_t *client, void *key, void *value)
+__client_ctx_get_int (client_t *client, void *key, void **value)
+{
+        int index = 0;
+        int ret   = 0;
+
+        for (index = 0; index < client->scratch_ctx.count; index++) {
+                if (client->scratch_ctx.ctx[index].ctx_key == key)
+                        break;
+        }
+
+        if (index == client->scratch_ctx.count) {
+                ret = -1;
+                goto out;
+        }
+
+        if (value)
+                *value = client->scratch_ctx.ctx[index].ctx_value;
+
+out:
+        return ret;
+}
+
+
+static int
+__client_ctx_set_int (client_t *client, void *key, void *value)
 {
         int index   = 0;
         int ret     = 0;
@@ -471,45 +495,31 @@ out:
 }
 
 
-int
+/*will return success with old value if exist*/
+void *
 client_ctx_set (client_t *client, void *key, void *value)
 {
         int ret = 0;
+        void *ret_value = NULL;
 
-        if (!client || !key)
-                return -1;
+        if (!client || !key || !value)
+                return NULL;
 
         LOCK (&client->scratch_ctx.lock);
         {
-                ret = client_ctx_set_int (client, key, value);
-        }
-        UNLOCK (&client->scratch_ctx.lock);
-
-        return ret;
-}
-
-
-static int
-client_ctx_get_int (client_t *client, void *key, void **value)
-{
-        int index = 0;
-        int ret   = 0;
-
-        for (index = 0; index < client->scratch_ctx.count; index++) {
-                if (client->scratch_ctx.ctx[index].ctx_key == key)
-                        break;
-        }
+                ret = __client_ctx_get_int (client, key, &ret_value);
+                if (!ret && ret_value) {
+                        UNLOCK (&client->scratch_ctx.lock);
+                        return ret_value;
+                }
 
-        if (index == client->scratch_ctx.count) {
-                ret = -1;
-                goto out;
+                ret = __client_ctx_set_int (client, key, value);
         }
+        UNLOCK (&client->scratch_ctx.lock);
 
-        if (value)
-                *value = client->scratch_ctx.ctx[index].ctx_value;
-
-out:
-        return ret;
+        if (ret)
+                return NULL;
+        return value;
 }
 
 
@@ -523,7 +533,7 @@ client_ctx_get (client_t *client, void *key, void **value)
 
         LOCK (&client->scratch_ctx.lock);
         {
-                ret = client_ctx_get_int (client, key, value);
+                ret = __client_ctx_get_int (client, key, value);
         }
         UNLOCK (&client->scratch_ctx.lock);
 
@@ -532,7 +542,7 @@ client_ctx_get (client_t *client, void *key, void **value)
 
 
 static int
-client_ctx_del_int (client_t *client, void *key, void **value)
+__client_ctx_del_int (client_t *client, void *key, void **value)
 {
         int index = 0;
         int ret   = 0;
@@ -568,7 +578,7 @@ client_ctx_del (client_t *client, void *key, void **value)
 
         LOCK (&client->scratch_ctx.lock);
         {
-                ret = client_ctx_del_int (client, key, value);
+                ret = __client_ctx_del_int (client, key, value);
         }
         UNLOCK (&client->scratch_ctx.lock);
 
diff --git a/libglusterfs/src/client_t.h b/libglusterfs/src/client_t.h
index 31f1bd048ed..b4546f36bea 100644
--- a/libglusterfs/src/client_t.h
+++ b/libglusterfs/src/client_t.h
@@ -101,7 +101,7 @@ gf_client_dump_inodes_to_dict (xlator_t *this, dict_t *dict);
 int
 gf_client_dump_inodes (xlator_t *this);
 
-int
+void *
 client_ctx_set (client_t *client, void *key, void *value);
 
 int