Re: [RFC 3/3] nvme: wire up support for async passthrough

[Keith Busch <kbusch@kernel.org>]

On Thu, Mar 04, 2021 at 04:31:11PM +0530, Kanchan Joshi wrote:
> On Thu, Mar 4, 2021 at 3:14 AM Chaitanya Kulkarni
> <Chaitanya.Kulkarni@wdc.com> wrote:
> >
> > On 3/2/21 23:22, Kanchan Joshi wrote:
> > > +     if (!ioucmd)
> > > +             cptr = &c;
> > > +     else {
> > > +             /*for async - allocate cmd dynamically */
> > > +             cptr = kmalloc(sizeof(struct nvme_command), GFP_KERNEL);
> > > +             if (!cptr)
> > > +                     return -ENOMEM;
> > > +     }
> > > +
> > > +     memset(cptr, 0, sizeof(c));
> > Why not kzalloc and remove memset() ?
> 
> Yes sure. Ideally I want to get rid of the allocation cost. Perhaps
> employing kmem_cache/mempool can help. Do you think there is a better
> way?

I'll need to think on this to consider if the memory cost is worth it
(8b to 64b), but you could replace nvme_request's 'struct nvme_command'
pointer with the struct itself and not have to allocate anything per IO.
An added bonus is that sync and async handling become more the same.