Revert "Prepare slice id eagerly to have a stable and predictable wri…

…te buffer usage" (juicedata#4720)

pkg/chunk/cached_store.go

@@ -412,9 +412,6 @@ func (s *wSlice) upload(indx int) {
 	blen := s.blockSize(indx)
 	key := s.key(indx)
 	pages := s.pages[indx]
-	if pages == nil {
-		panic(fmt.Sprintf("block #%d is nil, concurrent upload?", indx))
-	}
 	s.pages[indx] = nil
 	s.pendings++
 

pkg/vfs/writer.go

@@ -135,9 +135,6 @@ func (s *sliceWriter) write(ctx meta.Context, off uint32, data []uint8) syscall.
 		s.slen = off + uint32(len(data))
 	}
 	s.lastMod = time.Now()
-	if s.id == 0 {
-		go s.prepareID(ctx, false)
-	}
 	if s.slen == meta.ChunkSize {
 		s.freezed = true
 		go s.flushData()
@@ -148,6 +145,8 @@ func (s *sliceWriter) write(ctx meta.Context, off uint32, data []uint8) syscall.
 				logger.Warnf("write: chunk: %d off: %d %s", s.id, off, err)
 				return syscall.EIO
 			}
+		} else if int(off) <= f.w.blockSize {
+			go s.prepareID(ctx, false)
 		}
 	}
 	return 0