iostream-temp: If write() to temp file fails at any time, move it bac…

…k to memory.

Similarly to if the write() to temp fails during the initial move attempt.
This way even if write() fails due to out of disk space, it's not visible
to caller. An error message is logged in any case.

src/lib/iostream-temp.c

@@ -79,6 +79,36 @@ static int o_stream_temp_move_to_fd(struct temp_ostream *tstream)
 	return 0;
 }
 
+int o_stream_temp_move_to_memory(struct ostream *output)
+{
+	struct temp_ostream *tstream =
+		(struct temp_ostream *)output->real_stream;
+	unsigned char buf[IO_BLOCK_SIZE];
+	uoff_t offset = 0;
+	ssize_t ret = 0;
+
+	i_assert(tstream->buf == NULL);
+	tstream->buf = buffer_create_dynamic(default_pool, 8192);
+	while (offset < tstream->ostream.ostream.offset &&
+	       (ret = pread(tstream->fd, buf, sizeof(buf), offset)) > 0) {
+		if ((size_t)ret > tstream->ostream.ostream.offset - offset)
+			ret = tstream->ostream.ostream.offset - offset;
+		buffer_append(tstream->buf, buf, ret);
+		offset += ret;
+	}
+	if (ret < 0) {
+		/* not really expecting this to happen */
+		i_error("iostream-temp %s: read(%s*) failed: %m",
+			o_stream_get_name(&tstream->ostream.ostream),
+			tstream->temp_path_prefix);
+		tstream->ostream.ostream.stream_errno = EIO;
+		return -1;
+	}
+	i_close_fd(&tstream->fd);
+	tstream->ostream.fd = -1;
+	return 0;
+}
+
 static ssize_t
 o_stream_temp_fd_sendv(struct temp_ostream *tstream,
 		       const struct const_iovec *iov, unsigned int iov_count)
@@ -88,8 +118,18 @@ o_stream_temp_fd_sendv(struct temp_ostream *tstream,
 
 	for (i = 0; i < iov_count; i++) {
 		if (write_full(tstream->fd, iov[i].iov_base, iov[i].iov_len) < 0) {
-			tstream->ostream.ostream.stream_errno = errno;
-			return -1;
+			i_error("iostream-temp %s: write(%s*) failed: %m - moving to memory",
+				o_stream_get_name(&tstream->ostream.ostream),
+				tstream->temp_path_prefix);
+			if (o_stream_temp_move_to_memory(&tstream->ostream.ostream) < 0)
+				return -1;
+			for (; i < iov_count; i++) {
+				buffer_append(tstream->buf, iov[i].iov_base, iov[i].iov_len);
+				bytes += iov[i].iov_len;
+				tstream->ostream.ostream.offset += iov[i].iov_len;
+			}
+			i_assert(tstream->fd_tried);
+			return bytes;
 		}
 		bytes += iov[i].iov_len;
 		tstream->ostream.ostream.offset += iov[i].iov_len;

src/lib/iostream-temp.h

@@ -25,4 +25,7 @@ struct ostream *iostream_temp_create_sized(const char *temp_path_prefix,
 struct istream *iostream_temp_finish(struct ostream **output,
 				     size_t max_buffer_size);
 
+/* For internal testing: */
+int o_stream_temp_move_to_memory(struct ostream *output);
+
 #endif

src/lib/test-iostream-temp.c

@@ -48,6 +48,31 @@ static void test_iostream_temp_create_sized_disk(void)
 	test_end();
 }
 
+static void test_iostream_temp_create_write_error(void)
+{
+	struct ostream *output;
+
+	test_begin("iostream_temp_create_sized() write error");
+	output = iostream_temp_create_sized(".", 0, "test", 1);
+
+	test_assert(o_stream_send(output, "123", 3) == 3);
+	test_assert(o_stream_get_fd(output) != -1);
+	test_assert(output->offset == 3);
+	test_assert(o_stream_temp_move_to_memory(output) == 0);
+	test_assert(o_stream_get_fd(output) == -1);
+	test_assert(o_stream_send(output, "45", 2) == 2);
+	test_assert(output->offset == 5);
+
+	const unsigned char *data;
+	size_t size;
+	struct istream *input = iostream_temp_finish(&output, 128);
+	test_assert(i_stream_read_bytes(input, &data, &size, 5) == 1 &&
+		    memcmp(data, "12345", 5) == 0);
+	i_stream_destroy(&input);
+
+	test_end();
+}
+
 static void test_iostream_temp_istream(void)
 {
 	struct istream *input, *input2, *temp_input;
@@ -120,5 +145,6 @@ void test_iostream_temp(void)
 {
 	test_iostream_temp_create_sized_memory();
 	test_iostream_temp_create_sized_disk();
+	test_iostream_temp_create_write_error();
 	test_iostream_temp_istream();
 }