[PATCH RFC] nvme-pci: remove the unsed code in alloc_size

[Christoph Hellwig]

On Mon, Jul 06, 2020 at 03:53:05PM -0700, Chaitanya Kulkarni wrote:
> >From the initial implementation of NVMe SGL kernel support
> commit a7a7cbe353a5 ("nvme-pci: add SGL support") with addition of the
> commit 943e942e6266 ("nvme-pci: limit max IO size and segments to avoid
> high order allocations") now there is only caller left for
> nvme_pci_iod_alloc_size() which statically passes true for last
> parameter that calculates allocation size based on SGL since we need
> size of biggest command supported for mempool allocation.
> 
> This patch removes the helper functions nvme_pci_iod_alloc_size() and
> nvme_npages() used for allocation size calculation and open codes it
> into nvme_probe().

This is an obviously correct transformation, but I think the existing
code is a land mine.  I think we should change it to use the maximum
of either the PRP or SGL case to gurantee that we are on the safe
side.  Can you do that instead?