Enforce filesize limits

[wookie184]

Enforce a limit on file sizes when reading from tmpfs.

[coveralls]

coverage: 90.947% (+0.1%) from 90.845% when pulling 16b1a13e206fa34bfc7af05363d5e78742e26e40 on enforce-filesize-limits into 38885785334c5b77748f1b4767ef44124cb4dd3f on main.