Do not block reads by previous unfinished writes

blockstore.h

@@ -50,6 +50,7 @@ Input:
   - version == 0: read the last stable version,
   - version == UINT64_MAX: read the last version,
   - otherwise: read the newest version that is <= the specified version
+  - reads aren't guaranteed to return data from previous unfinished writes
   For writes:
   - if version == 0, a new version is assigned automatically
   - if version != 0, it is assigned for the new write if possible, otherwise -EINVAL is returned

blockstore_impl.cpp

@@ -258,19 +258,6 @@ void blockstore_impl_t::check_wait(blockstore_op_t *op)
         }
         PRIV(op)->wait_for = 0;
     }
-    else if (PRIV(op)->wait_for == WAIT_IN_FLIGHT)
-    {
-        auto dirty_it = dirty_db.find((obj_ver_id){
-            .oid = op->oid,
-            .version = PRIV(op)->wait_detail,
-        });
-        if (dirty_it != dirty_db.end() && IS_IN_FLIGHT(dirty_it->second.state))
-        {
-            // do not submit
-            return;
-        }
-        PRIV(op)->wait_for = 0;
-    }
     else if (PRIV(op)->wait_for == WAIT_JOURNAL)
     {
         if (journal.used_start == PRIV(op)->wait_detail)

blockstore_impl.h

@@ -128,8 +128,6 @@ struct __attribute__((__packed__)) dirty_entry
 
 // Suspend operation until there are more free SQEs
 #define WAIT_SQE 1
-// Suspend operation until version <wait_detail> of object <oid> is written
-#define WAIT_IN_FLIGHT 2
 // Suspend operation until there are <wait_detail> bytes of free space in the journal on disk
 #define WAIT_JOURNAL 3
 // Suspend operation until the next journal sector buffer is free

blockstore_read.cpp

@@ -8,12 +8,10 @@ int blockstore_impl_t::fulfill_read_push(blockstore_op_t *op, void *buf, uint64_
         // Zero-length version - skip
         return 1;
     }
-    if (IS_IN_FLIGHT(item_state))
+    else if (IS_IN_FLIGHT(item_state))
     {
-        // Pause until it's written somewhere
-        PRIV(op)->wait_for = WAIT_IN_FLIGHT;
-        PRIV(op)->wait_detail = item_version;
-        return 0;
+        // Write not finished yet - skip
+        return 1;
     }
     else if (IS_DELETE(item_state))
     {

blockstore_write.cpp

@@ -63,13 +63,14 @@ bool blockstore_impl_t::enqueue_write(blockstore_op_t *op)
         };
         enqueue_op(sync_op);
     }
-    // Immediately add the operation into dirty_db, so subsequent reads could see it
 #ifdef BLOCKSTORE_DEBUG
     if (is_del)
         printf("Delete %lu:%lu v%lu\n", op->oid.inode, op->oid.stripe, op->version);
     else
         printf("Write %lu:%lu v%lu offset=%u len=%u\n", op->oid.inode, op->oid.stripe, op->version, op->offset, op->len);
 #endif
+    // No strict need to add it into dirty_db here, it's just left
+    // from the previous implementation where reads waited for writes
     dirty_db.emplace((obj_ver_id){
         .oid = op->oid,
         .version = op->version,