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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id l31sm88186182pgm.63.2019.07.25.09.49.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 25 Jul 2019 09:49:32 -0700 (PDT) Date: Thu, 25 Jul 2019 09:50:15 -0700 From: Nicolin Chen To: Ezequiel Garcia Cc: hch@lst.de, robin.murphy@arm.com, Marek Szyprowski , vdumpa@nvidia.com, Russell King , Catalin Marinas , Will Deacon , chris@zankel.net, jcmvbkbc@gmail.com, joro@8bytes.org, David Woodhouse , Tony Lindgren , Andrew Morton , sfr@canb.auug.org.au, treding@nvidia.com, keescook@chromium.org, iamjoonsoo.kim@lge.com, wsa+renesas@sang-engineering.com, linux-arm-kernel , Linux Kernel Mailing List , linux-xtensa@linux-xtensa.org, iommu@lists.linux-foundation.org, dann.frazier@canonical.com, dafna.hirschfeld@collabora.com Subject: Re: [PATCH v3 1/2] dma-contiguous: Abstract dma_{alloc,free}_contiguous() Message-ID: <20190725165015.GA31961@Asurada-Nvidia.nvidia.com> References: <20190524040633.16854-1-nicoleotsuka@gmail.com> <20190524040633.16854-2-nicoleotsuka@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 25, 2019 at 01:06:42PM -0300, Ezequiel Garcia wrote: > I can't find a way to forward-redirect from Gmail, so I'm Ccing Dafna > who found a regression caused by this commit. Dafna, can you give all > the details, including the log and how you are reproducing it? I saw the conversation there. Sorry for not replying yet. May we discuss there since there are full logs available? Thanks Nicolin > > > On Fri, 24 May 2019 at 01:08, Nicolin Chen wrote: > > > > Both dma_alloc_from_contiguous() and dma_release_from_contiguous() > > are very simply implemented, but requiring callers to pass certain > > parameters like count and align, and taking a boolean parameter to > > check __GFP_NOWARN in the allocation flags. So every function call > > duplicates similar work: > > /* A piece of example */ > > unsigned long order = get_order(size); > > size_t count = size >> PAGE_SHIFT; > > page = dma_alloc_from_contiguous(dev, count, order, gfp & __GFP_NOWARN); > > [...] > > dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT); > > > > Additionally, as CMA can be used only in the context which permits > > sleeping, most of callers do a gfpflags_allow_blocking() check and > > a corresponding fallback allocation of normal pages upon any false > > result: > > /* A piece of example */ > > if (gfpflags_allow_blocking(flag)) > > page = dma_alloc_from_contiguous(); > > if (!page) > > page = alloc_pages(); > > [...] > > if (!dma_release_from_contiguous(dev, page, count)) > > __free_pages(page, get_order(size)); > > > > So this patch simplifies those function calls by abstracting these > > operations into the two new functions: dma_{alloc,free}_contiguous. > > > > As some callers of dma_{alloc,release}_from_contiguous() might be > > complicated, this patch just implements these two new functions to > > kernel/dma/direct.c only as an initial step. > > > > Suggested-by: Christoph Hellwig > > Signed-off-by: Nicolin Chen > > --- > > Changelog > > v2->v3: > > * Added missing "static inline" in header file to fix build error. > > v1->v2: > > * Added new functions beside the old ones so we can replace callers > > one by one later. > > * Applied new functions to dma/direct.c only, because it's the best > > example caller to apply and should be safe with the new functions. > > > > include/linux/dma-contiguous.h | 11 ++++++++ > > kernel/dma/contiguous.c | 48 ++++++++++++++++++++++++++++++++++ > > kernel/dma/direct.c | 24 +++-------------- > > 3 files changed, 63 insertions(+), 20 deletions(-) > > > > diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h > > index f247e8aa5e3d..00a370c1c140 100644 > > --- a/include/linux/dma-contiguous.h > > +++ b/include/linux/dma-contiguous.h > > @@ -115,6 +115,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count, > > unsigned int order, bool no_warn); > > bool dma_release_from_contiguous(struct device *dev, struct page *pages, > > int count); > > +struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp); > > +void dma_free_contiguous(struct device *dev, struct page *page, size_t size); > > > > #else > > > > @@ -157,6 +159,15 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages, > > return false; > > } > > > > +static inline > > +struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp) > > +{ > > + return NULL; > > +} > > + > > +static inline > > +void dma_free_contiguous(struct device *dev, struct page *page, size_t size) { } > > + > > #endif > > > > #endif > > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c > > index b2a87905846d..21f39a6cb04f 100644 > > --- a/kernel/dma/contiguous.c > > +++ b/kernel/dma/contiguous.c > > @@ -214,6 +214,54 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages, > > return cma_release(dev_get_cma_area(dev), pages, count); > > } > > > > +/** > > + * dma_alloc_contiguous() - allocate contiguous pages > > + * @dev: Pointer to device for which the allocation is performed. > > + * @size: Requested allocation size. > > + * @gfp: Allocation flags. > > + * > > + * This function allocates contiguous memory buffer for specified device. It > > + * first tries to use device specific contiguous memory area if available or > > + * the default global one, then tries a fallback allocation of normal pages. > > + */ > > +struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp) > > +{ > > + int node = dev ? dev_to_node(dev) : NUMA_NO_NODE; > > + size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT; > > + size_t align = get_order(PAGE_ALIGN(size)); > > + struct cma *cma = dev_get_cma_area(dev); > > + struct page *page = NULL; > > + > > + /* CMA can be used only in the context which permits sleeping */ > > + if (cma && gfpflags_allow_blocking(gfp)) { > > + align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT); > > + page = cma_alloc(cma, count, align, gfp & __GFP_NOWARN); > > + } > > + > > + /* Fallback allocation of normal pages */ > > + if (!page) > > + page = alloc_pages_node(node, gfp, align); > > + > > + return page; > > +} > > + > > +/** > > + * dma_free_contiguous() - release allocated pages > > + * @dev: Pointer to device for which the pages were allocated. > > + * @page: Pointer to the allocated pages. > > + * @size: Size of allocated pages. > > + * > > + * This function releases memory allocated by dma_alloc_contiguous(). As the > > + * cma_release returns false when provided pages do not belong to contiguous > > + * area and true otherwise, this function then does a fallback __free_pages() > > + * upon a false-return. > > + */ > > +void dma_free_contiguous(struct device *dev, struct page *page, size_t size) > > +{ > > + if (!cma_release(dev_get_cma_area(dev), page, size >> PAGE_SHIFT)) > > + __free_pages(page, get_order(size)); > > +} > > + > > /* > > * Support for reserved memory regions defined in device tree > > */ > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > > index 2c2772e9702a..0816c1e8b05a 100644 > > --- a/kernel/dma/direct.c > > +++ b/kernel/dma/direct.c > > @@ -96,8 +96,6 @@ static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) > > struct page *__dma_direct_alloc_pages(struct device *dev, size_t size, > > dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) > > { > > - unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT; > > - int page_order = get_order(size); > > struct page *page = NULL; > > u64 phys_mask; > > > > @@ -109,20 +107,9 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size, > > gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask, > > &phys_mask); > > again: > > - /* CMA can be used only in the context which permits sleeping */ > > - if (gfpflags_allow_blocking(gfp)) { > > - page = dma_alloc_from_contiguous(dev, count, page_order, > > - gfp & __GFP_NOWARN); > > - if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { > > - dma_release_from_contiguous(dev, page, count); > > - page = NULL; > > - } > > - } > > - if (!page) > > - page = alloc_pages_node(dev_to_node(dev), gfp, page_order); > > - > > + page = dma_alloc_contiguous(dev, size, gfp); > > if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { > > - __free_pages(page, page_order); > > + dma_free_contiguous(dev, page, size); > > page = NULL; > > > > if (IS_ENABLED(CONFIG_ZONE_DMA32) && > > @@ -154,7 +141,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, > > if (PageHighMem(page)) { > > /* > > * Depending on the cma= arguments and per-arch setup > > - * dma_alloc_from_contiguous could return highmem pages. > > + * dma_alloc_contiguous could return highmem pages. > > * Without remapping there is no way to return them here, > > * so log an error and fail. > > */ > > @@ -176,10 +163,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, > > > > void __dma_direct_free_pages(struct device *dev, size_t size, struct page *page) > > { > > - unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT; > > - > > - if (!dma_release_from_contiguous(dev, page, count)) > > - __free_pages(page, get_order(size)); > > + dma_free_contiguous(dev, page, size); > > } > > > > void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr, > > -- > > 2.17.1 > >