Ceph

When using the rados_aio_read() interface the c.bl bufferlist stores the read data. So the code below will set rval = c.bl.length(). The aio_read() gets a user bufferlist passed in, so return_value() returns 0 on success. This is just a confusing behavior which should be consistent between rados_return_value() and ctx.return_value().

void librados::IoCtxImpl::C_aio_Ack::finish(int r)
{
  c->lock.Lock();
  c->rval = r;
  c->ack = true;
  if (c->is_read)
    c->safe = true;
  c->cond.Signal();

  if (c->bl.length() > 0) {
    c->rval = c->bl.length();
  }

  if (c->callback_complete) {
    c->io->client->finisher.queue(new C_AioComplete(c));
  }
  if (c->is_read && c->callback_safe) {
    c->io->client->finisher.queue(new C_AioSafe(c));
  }

  c->put_unlock();
}