fix stalled pieces on disk-full errors

ChangeLog

@@ -1,3 +1,4 @@
+	* fix stalled pieces on disk-full errors
 	* fix build configuration issue on NetBSD, OpenBSD and DragonFly
 	* make UTF-8 sanitization a bit stricter. This will re-write invalid UTF-8
 	  code points encoding surrogate pairs

src/piece_picker.cpp

@@ -1056,7 +1056,7 @@ namespace libtorrent {
 		std::cerr << "[" << this << "] " << "restore_piece(" << index << ")" << std::endl;
 #endif
 		auto const download_state = m_piece_map[index].download_queue();
-		TORRENT_ASSERT(download_state != piece_pos::piece_open);
+		// if the piece was cancelled, it may have been removed
 		if (download_state == piece_pos::piece_open) return;
 
 		auto i = find_dl_piece(download_state, index);
@@ -3407,7 +3407,7 @@ get_out:
 	// TODO: 2 it would be nice if this could be folded into lock_piece()
 	// the main distinction is that this also maintains the m_num_passed
 	// counter and the passed_hash_check member
-	// Is there ever a case where we call write filed without also locking
+	// Is there ever a case where we call write failed without also locking
 	// the piece? Perhaps write_failed() should imply locking it.
 	void piece_picker::write_failed(piece_block const block)
 	{

src/torrent.cpp

@@ -1234,10 +1234,19 @@ bool is_downloading_state(int const st)
 		pause();
 	}
 
-	void torrent::on_piece_fail_sync(piece_index_t, piece_block) try
+	void torrent::on_piece_fail_sync(piece_index_t const piece, piece_block) try
 	{
 		if (m_abort) return;
 
+		// the user may have called force_recheck, which clears
+		// the piece picker
+		if (has_picker())
+		{
+			// unlock the piece and restore it, as if no block was
+			// ever downloaded for it.
+			m_picker->restore_piece(piece);
+		}
+
 		update_gauge();
 		// some peers that previously was no longer interesting may
 		// now have become interesting, since we lack this one piece now.