Here is nifty table that I use to calculate the optimal resolution. The idea behind it is that the viewer is standing in such distance that he can see whole picture. (so the 10x10m is billboard while 1x2 is rollup) This is for solvent printing
You probably looked at that table and think: oh no, but mu picture should have 72 dpi and I only have 34!
But don't worry, remember that the dot for big prints are not crisp as in offset printing.
So do not hesitate to upscale the resolution. If you are afraid of the look do a simply action in photoshop that will upscale the photo by 10% so you will have more control over the outcome and can came in with sharpen filter.
Have in mind that the mayor role play what is on the photo. If you have some trees, grass, waterfall on it I wouldn't be afraid to print it even with 10 DPI.
But if you have something that have clear lines, strong contrast between colors then you should pay bigger attention to those places.