From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Sat, 27 Apr 2013 11:54:52 +0000 (+0200)
Subject: Never send more than IOV_MAX (1024) iovecs in pwritev.
X-Git-Tag: 1.0.0~39
X-Git-Url: https://git.sesse.net/?p=cubemap;a=commitdiff_plain;h=ea11d357cc010351871392e433880fb2401161b2;hp=6cb6815facd386521b21c66c35b48ea295dff98e

Never send more than IOV_MAX (1024) iovecs in pwritev.

This fixes issues with “pwritev: Invalid argument” showing up
under rare circumstances. Apparently the glibc wrapper workaround
described in writev(2) does not work, or does not work for pwritev().
---

diff --git a/stream.cpp b/stream.cpp
index 0c0faba..e8d65db 100644
--- a/stream.cpp
+++ b/stream.cpp
@@ -1,5 +1,6 @@
 #include <assert.h>
 #include <errno.h>
+#include <limits.h>
 #include <netinet/in.h>
 #include <stdlib.h>
 #include <string.h>
@@ -129,7 +130,8 @@ void Stream::put_client_to_sleep(Client *client)
 vector<iovec> collect_iovecs(const vector<iovec> &data, size_t bytes_wanted)
 {
 	vector<iovec> ret;
-	for (size_t i = 0; i < data.size() && bytes_wanted > 0; ++i) {
+	size_t max_iovecs = std::min<size_t>(data.size(), IOV_MAX);
+	for (size_t i = 0; i < max_iovecs && bytes_wanted > 0; ++i) {
 		if (data[i].iov_len <= bytes_wanted) {
 			// Consume the entire iovec.
 			ret.push_back(data[i]);