Make blockstore list operation return consistent snapshots

blockstore_impl.cpp

@@ -145,7 +145,7 @@ void blockstore_impl_t::loop()
             }
             unsigned ring_space = ringloop->space_left();
             unsigned prev_sqe_pos = ringloop->save();
-            int dequeue_op = 0;
+            bool dequeue_op = false;
             if (op->opcode == BS_OP_READ)
             {
                 dequeue_op = dequeue_read(op);
@@ -175,16 +175,33 @@ void blockstore_impl_t::loop()
             }
             else if (op->opcode == BS_OP_STABLE)
             {
+                if (has_writes == 2)
+                {
+                    // Don't submit additional flushes before completing previous LISTs
+                    break;
+                }
                 dequeue_op = dequeue_stable(op);
             }
             else if (op->opcode == BS_OP_ROLLBACK)
             {
+                if (has_writes == 2)
+                {
+                    // Don't submit additional flushes before completing previous LISTs
+                    break;
+                }
                 dequeue_op = dequeue_rollback(op);
             }
             else if (op->opcode == BS_OP_LIST)
             {
-                process_list(op);
-                dequeue_op = true;
+                // Block LIST operation by previous modifications,
+                // so it always returns a consistent state snapshot
+                if (has_writes == 2 || inflight_writes > 0)
+                    has_writes = 2;
+                else
+                {
+                    process_list(op);
+                    dequeue_op = true;
+                }
             }
             if (dequeue_op)
             {

blockstore_impl.h

@@ -230,6 +230,7 @@ class blockstore_impl_t
 
     bool live = false, queue_stall = false;
     ring_loop_t *ringloop;
+    int inflight_writes = 0;
 
     bool stop_sync_submitted;
 

blockstore_rollback.cpp

@@ -18,6 +18,10 @@ int blockstore_impl_t::dequeue_rollback(blockstore_op_t *op)
         });
         if (dirty_it == dirty_db.begin())
         {
+            if (v->version == 0)
+            {
+                // Already rolled back
+            }
         bad_op:
             op->retval = -EINVAL;
             FINISH_OP(op);
@@ -115,6 +119,7 @@ int blockstore_impl_t::dequeue_rollback(blockstore_op_t *op)
     PRIV(op)->max_flushed_journal_sector = 1 + journal.cur_sector;
     PRIV(op)->pending_ops = s;
     PRIV(op)->op_state = 1;
+    inflight_writes++;
     return 1;
 }
 
@@ -175,6 +180,7 @@ resume_5:
             erase_dirty(rm_start, rm_end, UINT64_MAX);
     }
     journal.trim();
+    inflight_writes--;
     // Acknowledge op
     op->retval = 0;
     FINISH_OP(op);
@@ -186,6 +192,7 @@ void blockstore_impl_t::handle_rollback_event(ring_data_t *data, blockstore_op_t
     live = true;
     if (data->res != data->iov.iov_len)
     {
+        inflight_writes--;
         throw std::runtime_error(
             "write operation failed ("+std::to_string(data->res)+" != "+std::to_string(data->iov.iov_len)+
             "). in-memory state is corrupted. AAAAAAAaaaaaaaaa!!!111"

blockstore_stable.cpp

@@ -108,6 +108,7 @@ int blockstore_impl_t::dequeue_stable(blockstore_op_t *op)
     }
     for (i = 0, v = (obj_ver_id*)op->buf; i < op->len; i++, v++)
     {
+        // FIXME: Only stabilize versions that aren't stable yet
         auto unstab_it = unstable_writes.find(v->oid);
         if (unstab_it != unstable_writes.end() &&
             unstab_it->second <= v->version)
@@ -132,6 +133,7 @@ int blockstore_impl_t::dequeue_stable(blockstore_op_t *op)
     PRIV(op)->max_flushed_journal_sector = 1 + journal.cur_sector;
     PRIV(op)->pending_ops = s;
     PRIV(op)->op_state = 1;
+    inflight_writes++;
     return 1;
 }
 
@@ -209,6 +211,7 @@ resume_5:
             flusher->enqueue_flush(*v);
         }
     }
+    inflight_writes--;
     // Acknowledge op
     op->retval = 0;
     FINISH_OP(op);
@@ -220,6 +223,7 @@ void blockstore_impl_t::handle_stable_event(ring_data_t *data, blockstore_op_t *
     live = true;
     if (data->res != data->iov.iov_len)
     {
+        inflight_writes--;
         throw std::runtime_error(
             "write operation failed ("+std::to_string(data->res)+" != "+std::to_string(data->iov.iov_len)+
             "). in-memory state is corrupted. AAAAAAAaaaaaaaaa!!!111"

blockstore_write.cpp

@@ -276,6 +276,7 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
             PRIV(op)->op_state = 3;
         }
     }
+    inflight_writes++;
     return 1;
 }
 
@@ -357,6 +358,7 @@ resume_4:
             dirty_it++;
         }
     }
+    inflight_writes--;
     // Acknowledge write
     op->retval = op->len;
     FINISH_OP(op);
@@ -368,6 +370,7 @@ void blockstore_impl_t::handle_write_event(ring_data_t *data, blockstore_op_t *o
     live = true;
     if (data->res != data->iov.iov_len)
     {
+        inflight_writes--;
         // FIXME: our state becomes corrupted after a write error. maybe do something better than just die
         throw std::runtime_error(
             "write operation failed ("+std::to_string(data->res)+" != "+std::to_string(data->iov.iov_len)+