libtorrent sync 1419

libtorrent/include/libtorrent/peer_connection.hpp

@@ -74,9 +74,6 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/socket_type.hpp"
 #include "libtorrent/intrusive_ptr_base.hpp"
 
-// TODO: each time a block is 'taken over'
-// from another peer. That peer must be given
-// a chance to become not-interested.
 
 namespace libtorrent
 {
@@ -701,6 +698,9 @@ namespace libtorrent
 		// a timestamp when the remote download rate
 		// was last updated
 		ptime m_remote_dl_update;
+        // the number of bytes send to the disk-io
+        // thread that hasn't yet been completely written.
+        int m_outstanding_writing_bytes;
 		
 #ifndef NDEBUG
 	public:

libtorrent/include/libtorrent/session_settings.hpp

@@ -108,6 +108,7 @@ namespace libtorrent
 			, unchoke_interval(20)
 			, num_want(200)
 			, initial_picker_threshold(4)
+			, max_outstanding_disk_bytes_per_connection(128 * 1024)
 #ifndef TORRENT_DISABLE_DHT
 			, use_dht_as_fallback(true)
 #endif
@@ -250,7 +251,15 @@ namespace libtorrent
 		// while we have fewer pieces than this, pick
 		// random pieces instead of rarest first.
 		int initial_picker_threshold;
-
+		
+        // the maximum number of bytes a connection may have
+        // pending in the disk write queue before its download
+        // rate is being throttled. This prevents fast downloads
+        // to slow medias to allocate more and more memory
+        // indefinitely. This should be set to at least 32 kB
+        // to not completely disrupt normal downloads.
+        int max_outstanding_disk_bytes_per_connection;
+                 
 #ifndef TORRENT_DISABLE_DHT
 		// while this is true, the dht will note be used unless the
 		// tracker is online

libtorrent/src/peer_connection.cpp

@@ -116,6 +116,7 @@ namespace libtorrent
 		, m_remote_bytes_dled(0)
 		, m_remote_dl_rate(0)
 		, m_remote_dl_update(time_now())
+		, m_outstanding_writing_bytes(0)
 #ifndef NDEBUG
 		, m_in_constructor(true)
 #endif
@@ -189,6 +190,7 @@ namespace libtorrent
 		, m_remote_bytes_dled(0)
 		, m_remote_dl_rate(0)
 		, m_remote_dl_update(time_now())
+        , m_outstanding_writing_bytes(0)
 #ifndef NDEBUG
 		, m_in_constructor(true)
 #endif
@@ -1150,6 +1152,7 @@ namespace libtorrent
 		
 		fs.async_write(p, data, bind(&peer_connection::on_disk_write_complete
 			, self(), _1, _2, p, t));
+        m_outstanding_writing_bytes += p.length;
 		picker.mark_as_writing(block_finished, peer_info_struct());
 	}
 
@@ -1158,6 +1161,12 @@ namespace libtorrent
 	{
 		session_impl::mutex_t::scoped_lock l(m_ses.m_mutex);
 
+        m_outstanding_writing_bytes -= p.length;
+        assert(m_outstanding_writing_bytes >= 0);
+        // in case the outstanding bytes just dropped down
+        // to allow to receive more data
+        setup_receive();
+
 		if (ret == -1 || !t)
 		{
 			if (!t)
@@ -2338,7 +2347,9 @@ namespace libtorrent
 			|| !m_send_buffer[(m_current_send_buffer + 1) & 1].empty())
 			&& (m_bandwidth_limit[upload_channel].quota_left() > 0
 				|| m_ignore_bandwidth_limits)
-			&& !m_connecting;
+			&& !m_connecting
+			&& m_outstanding_writing_bytes < 
+			        m_ses.settings().max_outstanding_disk_bytes_per_connection;
 	}
 
 	bool peer_connection::can_read() const