Refine comments

src/cluster.c

@@ -1634,17 +1634,17 @@ void sflushCommand(client *c) {
 
     /* Verify slotsToFlushRq[] covers ALL slots of myNode. */
     clusterNode *myNode = getMyClusterNode();
-    /* During iteration trace also the slot range pairs and save in SlotsFlush
-     * Allocated on heap since there is a chance that FLUSH SYNC will be run as
-     * blocking ASYNC and only later reply with slot ranges */
+    /* During iteration trace also the slot range pairs and save in SlotsFlush.
+     * It is allocated on heap since there is a chance that FLUSH SYNC will be 
+     * running as blocking ASYNC and only later reply with slot ranges */
     int capacity = 32; /* Initial capacity */
     SlotsFlush *sflush = zmalloc(sizeof(SlotsFlush) + sizeof(SlotRange) * capacity);
     sflush->numRanges = 0;
     int inSlotRange = 0;
     for (int i = 0; i < CLUSTER_SLOTS; i++) {
         if (myNode == getNodeBySlot(i)) {
             if (!slotsToFlushRq[i]) {
-                addReplySetLen(c, 0); /* Not all slots of my node got covered */
+                addReplySetLen(c, 0); /* Not all slots of mynode got covered. See sflushCommand() comment. */
                 zfree(sflush);
                 return;
             }

src/db.c

@@ -732,7 +732,7 @@ void flushAllDataAndResetRDB(int flags) {
  * Utilized by commands SFLUSH, FLUSHALL and FLUSHDB.
  */
 void flushallSyncBgDone(uint64_t client_id, void *sflush) {
-    SlotsFlush *slotFlush = (SlotsFlush *)sflush;
+    SlotsFlush *slotsFlush = (SlotsFlush *)sflush;
     client *c = lookupClientByID(client_id);
 
     /* Verify that client still exists */
@@ -746,11 +746,10 @@ void flushallSyncBgDone(uint64_t client_id, void *sflush) {
     updateStatsOnUnblock(c, 0 /*blocked_us*/, elapsedUs(c->bstate.lazyfreeStartTime), 0);
 
     /* Only SFLUSH command pass pointer to `SlotsFlush` */
-    if (slotFlush) {
-        replySlotsFlush(c, slotFlush);
-    } else {
+    if (slotsFlush)
+        replySlotsFlush(c, slotsFlush);
+    else
         addReply(c, shared.ok);
-    }
 
     /* mark client as unblocked */
     unblockClient(c, 1);
@@ -770,10 +769,12 @@ void flushallSyncBgDone(uint64_t client_id, void *sflush) {
  * Return 1 indicates that flush SYNC is actually running in bg as blocking ASYNC
  * Return 0 otherwise
  *
- * sflush - provided only by SFLUSH command, otherwise NULL
+ * sflush - provided only by SFLUSH command, otherwise NULL. Will be used on 
+ *          completion to reply with the slots flush result. Ownership is passed
+ *          to the completion job in case of `blocking_async`.
  */
 int flushCommandCommon(client *c, int type, int flags, SlotsFlush *sflush) {
-    int blocking_async = 0; /* FLUSHALL\FLUSHDB SYNC opt to run as blocking ASYNC */
+    int blocking_async = 0; /* Flush SYNC option to run as blocking ASYNC */
 
     /* in case of SYNC, check if we can optimize and run it in bg as blocking ASYNC */
     if ((!(flags & EMPTYDB_ASYNC)) && (!(c->flags & CLIENT_AVOID_BLOCKING_ASYNC_FLUSH))) {