Re: [RFC PATCH v2 04/11] PCI/P2PDMA: Introduce pci_p2pdma_should_map_bus() and pci_p2pdma_bus_offset()

[Jason Gunthorpe]

On Mon, Mar 15, 2021 at 10:27:08AM -0600, Logan Gunthorpe wrote:

> In this case the WARN_ON is just to guard against misuse of the
> function. It should never happen unless a developer changes the code in
> a way that is incorrect. So I think that's the correct use of WARN_ON.
> Though I might change it to WARN and return, that seems safer.

Right, WARN_ON and return is the right pattern for an assertion that
must never happen:

  if (WARN_ON(foo))
      return -1

Linus wants assertions like this to be able to recover. People runing
the 'panic on warn' mode want the kernel to stop if it detects an
internal malfunction.

Jason