Re: [PATCH] PCI/MSI: preference to returning -ENOSPC from pci_alloc_irq_vectors_affinity

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Jan 15, 2019 at 09:22:45AM -0700, Jens Axboe wrote:
> On 1/15/19 6:11 AM, Christoph Hellwig wrote:
> > On Mon, Jan 14, 2019 at 05:23:39PM -0600, Bjorn Helgaas wrote:
> >> Applied to pci/msi for v5.1, thanks!
> >>
> >> If this is something that should be in v5.0, let me know and include the
> >> justification, e.g., something we already merged for v5.0 or regression
> >> info, etc, and a Fixes: line, and I'll move it to for-linus.
> > 
> > I'd be tempted to queues this up for 5.0.  Ming, what is your position?
> 
> I think we should - the API was introduced in this series, I think there's
> little (to no) reason NOT to fix it for 5.0.

I'm guessing the justification goes something like this (I haven't
done all the research, so I'll leave it to Ming to fill in the details):

  pci_alloc_irq_vectors_affinity() was added in v4.x by XXXX ("...").
  It had this return value defect then, but its min_vecs/max_vecs
  parameters removed the need for callers to interatively reduce the
  number of IRQs requested and retry the allocation, so they didn't
  need to distinguish -ENOSPC from -EINVAL.

  In v5.0, XXX ("...") added IRQ sets to the interface, which
  reintroduced the need to check for -ENOSPC and possibly reduce the
  number of IRQs requested and retry the allocation.