streams: support unlimited synchronous cork/uncork cycles

net streams can request multiple chunks to be written in a synchronous
fashion. If this is combined with cork/uncork, en error is currently
thrown because of a regression introduced in:
https://github.com/nodejs/node/commit/89aeab901ac9e34c79be3854f1aa41f2a4fb6888
(https://github.com/nodejs/node/pull/4354).

Fixes: https://github.com/nodejs/node/issues/6154
PR-URL: https://github.com/nodejs/node/pull/6164
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Mathias Buus <mathiasbuus@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/lib/_stream_writable.js b/lib/_stream_writable.js
index b6e621fd1e..98ca05da39 100644
--- a/lib/_stream_writable.js
+++ b/lib/_stream_writable.js
@@ -112,10 +112,9 @@ function WritableState(options, stream) {
   // count buffered requests
   this.bufferedRequestCount = 0;
 
-  // create the two objects needed to store the corked requests
-  // they are not a linked list, as no new elements are inserted in there
+  // allocate the first CorkedRequest, there is always
+  // one allocated and free to use, and we maintain at most two
   this.corkedRequestsFree = new CorkedRequest(this);
-  this.corkedRequestsFree.next = new CorkedRequest(this);
 }
 
 WritableState.prototype.getBuffer = function writableStateGetBuffer() {
@@ -387,12 +386,16 @@ function clearBuffer(stream, state) {
 
     doWrite(stream, state, true, state.length, buffer, '', holder.finish);
 
-    // doWrite is always async, defer these to save a bit of time
+    // doWrite is almost always async, defer these to save a bit of time
     // as the hot path ends with doWrite
     state.pendingcb++;
     state.lastBufferedRequest = null;
-    state.corkedRequestsFree = holder.next;
-    holder.next = null;
+    if (holder.next) {
+      state.corkedRequestsFree = holder.next;
+      holder.next = null;
+    } else {
+      state.corkedRequestsFree = new CorkedRequest(state);
+    }
   } else {
     // Slow case, write chunks one-by-one
     while (entry) {