+
+int read_subbuffer(struct fd_pair *pair)
+{
+ unsigned int consumed_old;
+ int err, ret;
+
+
+ err = ioctl(pair->channel, RELAYFS_GET_SUBBUF,
+ &consumed_old);
+ printf("cookie : %u\n", consumed_old);
+ if(err != 0) {
+ perror("Error in reserving sub buffer");
+ ret = -EPERM;
+ goto get_error;
+ }
+
+ err = TEMP_FAILURE_RETRY(write(pair->trace,
+ pair->mmap + (consumed_old & (~(pair->subbuf_size-1))),
+ pair->subbuf_size));
+
+ if(err < 0) {
+ perror("Error in writing to file");
+ ret = err;
+ goto write_error;
+ }
+
+
+write_error:
+ err = ioctl(pair->channel, RELAYFS_PUT_SUBBUF, &consumed_old);
+ if(err != 0) {
+ if(errno == -EFAULT) {
+ perror("Error in unreserving sub buffer");
+ ret = -EFAULT;
+ } else if(errno == -EIO) {
+ perror("Reader has been pushed by the writer, last subbuffer corrupted.");
+ /* FIXME : we may delete the last written buffer if we wish. */
+ ret = -EIO;
+ }
+ goto get_error;
+ }
+
+get_error:
+ return ret;
+}
+
+