Re: [PATCH 2/2] nvme-pci: use dma_alloc_noncontigous if possible

[Leon Romanovsky <leon@kernel.org>]

On Mon, Dec 02, 2024 at 12:15:49PM -0700, Keith Busch wrote:
> On Mon, Dec 02, 2024 at 09:05:41PM +0200, Leon Romanovsky wrote:
> > I see at least two possible solutions, add GFP_NOWARN in nvme_alloc_host_mem_single()
> > or the following patch:
> > 
> > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> > index 4c644bb7f069..baed4059d8a5 100644
> > --- a/drivers/nvme/host/pci.c
> > +++ b/drivers/nvme/host/pci.c
> > @@ -2172,7 +2172,8 @@ static int nvme_alloc_host_mem_multi(struct nvme_dev *dev, u64 preferred,
> > 
> >  static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
> >  {
> > -       u64 min_chunk = min_t(u64, preferred, PAGE_SIZE * MAX_ORDER_NR_PAGES);
> > +       u64 max_chunk = PAGE_SIZE * MAX_ORDER_NR_PAGES;
> > +       u64 min_chunk = min_t(u64, preferred, max_chunk);
> >         u64 hmminds = max_t(u32, dev->ctrl.hmminds * 4096, PAGE_SIZE * 2);
> >         u64 chunk_size;
> > 
> > @@ -2180,7 +2181,7 @@ static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
> >          * If there is an IOMMU that can merge pages, try a virtually
> >          * non-contiguous allocation for a single segment first.
> >          */
> > -       if (!(PAGE_SIZE & dma_get_merge_boundary(dev->dev))) {
> > +       if (!(PAGE_SIZE & dma_get_merge_boundary(dev->dev)) && preferred < max_chunk) {
> >                 if (!nvme_alloc_host_mem_single(dev, preferred))
> >                         return 0;
> >         }
> > (END)
> > 
> > What is the preferred way to overcome the warning?
> 
> I think your max_chunk check suggestion looks pretty good.

Awesome, will send proper patch tomorrow.

Thanks