When reading source images that come in linear colour space:, normally you will apply an Unicolour node to convert to the desired curve and gammut. 

But one important note on working with Linear Light files:  It's always a good idea to avoid any image scaling while the image has a Linear Light curve.  This is because most scaling algorithms (like Bicubic, or Mistika's Taps filters) add a very small element of contrast enhancement in the scaling process, and because the values in a Linear image are obviously very high contrast to begin with, the scaling can cause the contrast to overshoot causing artifacts.  As a general rule, always convert to a more suitable space (like a Log curve) to do scaling, then convert back to Linear Light at the end of the process if that's what you need to deliver.