Re: [PATCH 2/3] lightnvm: encapsule rqd dma allocations

[Matias BjÃrling]

On 08/29/2018 03:41 PM, Javier Gonzalez wrote:
> > On 29 Aug 2018, at 15.36, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> >
> > On 08/29/2018 03:18 PM, Javier Gonzalez wrote:
> > > > On 29 Aug 2018, at 15.00, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> > > >
> > > > On 08/29/2018 10:56 AM, Javier GonzÃlez wrote:
> > > > > dma allocations for ppa_list and meta_list in rqd are replicated in
> > > > > several places across the pblk codebase. Make helpers to encapsulate
> > > > > creation and deletion to simplify the code.
> > > > > Signed-off-by: Javier GonzÃlez <javier@xxxxxxxxxxxx>
> > > > > ---
> > > > >   drivers/lightnvm/pblk-core.c     | 69 +++++++++++++++++++++++++---------------
> > > > >   drivers/lightnvm/pblk-read.c     | 35 ++++++++++----------
> > > > >   drivers/lightnvm/pblk-recovery.c | 29 ++++++-----------
> > > > >   drivers/lightnvm/pblk-write.c    | 15 ++-------
> > > > >   drivers/lightnvm/pblk.h          |  3 ++
> > > > >   5 files changed, 74 insertions(+), 77 deletions(-)
> > > > > diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> > > > > index 09160ec02c5f..767178185f19 100644
> > > > > --- a/drivers/lightnvm/pblk-core.c
> > > > > +++ b/drivers/lightnvm/pblk-core.c
> > > > > @@ -237,6 +237,34 @@ static void pblk_invalidate_range(struct pblk *pblk, sector_t slba,
> > > > >   	spin_unlock(&pblk->trans_lock);
> > > > >   }
> > > > >   +int pblk_setup_rqd(struct pblk *pblk, struct nvm_rq *rqd, gfp_t mem_flags,
> > > > > +		   bool is_vector)
> > > >
> > > >
> > > > The mem_flags argument can be removed. It is GFP_KERNEL from all the
> > > > places it is called.
> > > Thought it was better to have the flexibility in a helper function, but
> > > we can always add it later on if needed...
> > > > is_vector, will be better to do nr_ppas (or similar name). Then
> > > > pblk_submit_read/pblk_submit_read_gc are a bit cleaner.
> > > We can do that too, yes.
> > > > > +{
> > > > > +	struct nvm_tgt_dev *dev = pblk->dev;
> > > > > +
> > > > > +	rqd->meta_list = nvm_dev_dma_alloc(dev->parent, mem_flags,
> > > > > +							&rqd->dma_meta_list);
> > > > > +	if (!rqd->meta_list)
> > > > > +		return -ENOMEM;
> > > > > +
> > > > > +	if (!is_vector)
> > > > > +		return 0;
> > > > > +
> > > > > +	rqd->ppa_list = rqd->meta_list + pblk_dma_meta_size;
> > > > > +	rqd->dma_ppa_list = rqd->dma_meta_list + pblk_dma_meta_size;
> > > >
> > > > Wrt to is_vector, does it matter if we just set ppa_list and
> > > > dma_ppa_list? If we have them, we use them, else leave them alone?
> > > If we only have 1 address then ppa_addr is set and the ppa_list attempt
> > > to free in the completion path interpreting ppa_addr as the dma address.
> > > So I don't think so - unless I'm missing something?
> >
> > In that case, we could drop is_vector/nr_ppas all together? That would be nice.
>
> The problem is that the metadata region still needs to be used, even if
> the ppa_list is not set. Thing that the oob area can be larger than
> 64bits, so we cannot do the dma address is the actual value trick.
>
> So if encapsulating, we need to know if we need to allocate the ppa_list
> or not.
>
> Does it make sense?

Cool. We'll just leave it as is.