> -----Original Message-----
> From: Christoph Hellwig [mailto:[email protected]]
> Sent: Thursday, July 23, 2020 2:30 AM
> To: Song Bao Hua (Barry Song) <[email protected]>
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected];
> [email protected]; [email protected]; Linuxarm
> <[email protected]>; [email protected];
> [email protected]; Jonathan Cameron
> <[email protected]>; Nicolas Saenz Julienne
> <[email protected]>; Steve Capper <[email protected]>; Andrew
> Morton <[email protected]>; Mike Rapoport <[email protected]>
> Subject: Re: [PATCH v3 1/2] dma-direct: provide the ability to reserve
> per-numa CMA
>
+cc Prime and Daode who are interested in this patchset.
> On Sun, Jun 28, 2020 at 11:12:50PM +1200, Barry Song wrote:
> > struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t
> gfp)
> > {
> > size_t count = size >> PAGE_SHIFT;
> > struct page *page = NULL;
> > struct cma *cma = NULL;
> > + int nid = dev ? dev_to_node(dev) : NUMA_NO_NODE;
> > + bool alloc_from_pernuma = false;
> > +
> > + if ((count <= 1) && !(dev && dev->cma_area))
> > + return NULL;
> >
> > if (dev && dev->cma_area)
> > cma = dev->cma_area;
> > - else if (count > 1)
> > + else if ((nid != NUMA_NO_NODE) &&
> dma_contiguous_pernuma_area[nid]
> > + && !(gfp & (GFP_DMA | GFP_DMA32))) {
> > + cma = dma_contiguous_pernuma_area[nid];
> > + alloc_from_pernuma = true;
> > + } else {
> > cma = dma_contiguous_default_area;
> > + }
>
> I find the function rather confusing now. What about something
> like (this relies on the fact that dev should never be NULL in the
> DMA API)
>
> struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
> {
> size_t cma_align = min_t(size_t, get_order(size),
> CONFIG_CMA_ALIGNMENT);
> size_t count = size >> PAGE_SHIFT;
>
> if (gfpflags_allow_blocking(gfp))
> return NULL;
> gfp &= __GFP_NOWARN;
>
> if (dev->cma_area)
I got a kernel robot warning which said dev should be checked before being
accessed
when I did a similar change in v1. Probably it was an invalid warning if dev
should
never be null.
> return cma_alloc(dev->cma_area, count, cma_align, gfp);
> if (count <= 1)
> return NULL;
>
> if (IS_ENABLED(CONFIG_PERNODE_CMA) && !(gfp & (GFP_DMA |
> GFP_DMA32)) {
> int nid = dev_to_node(dev);
> struct cma *cma = dma_contiguous_pernuma_area[nid];
> struct page *page;
>
> if (cma) {
> page = cma_alloc(cma, count, cma_align, gfp);
> if (page)
> return page;
> }
> }
>
> return cma_alloc(dma_contiguous_default_area, count, cma_align, gfp);
> }
Yes, it looks much better.
>
> > + /*
> > + * otherwise, page is from either per-numa cma or default cma
> > + */
> > + int nid = page_to_nid(page);
> > +
> > + if (nid != NUMA_NO_NODE) {
> > + if (cma_release(dma_contiguous_pernuma_area[nid], page,
> > + PAGE_ALIGN(size) >> PAGE_SHIFT))
> > + return;
> > + }
> > +
> > + if (cma_release(dma_contiguous_default_area, page,
>
> How can page_to_nid ever return NUMA_NO_NODE?
I thought page_to_nid would return NUMA_NO_NODE if CONFIG_NUMA is
not enabled. Probably I was wrong. Will get it fixed in v4.
Thanks
Barry
