[$] Really fixing getrandom()

The final days of the 5.3 kernel development cycle included an extensive discussion of thegetrandom() API and the reversion of an ext4 improvement thatwas indirectly causing boot hangs due to a lack of entropy. Blockingfilesystem improvements because they are too effective is clearly not agood long-term development strategy for the kernel, so there was aconsensus that some sort of better solution had to be found. What was lackingwas an idea of what that solution should be. It is thus surprising thatthe problem appears to have been dealt with in 5.4 with little in the wayof dissent or disagreement.