From: dann frazier <dann.frazier@canonical.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
Robin Murphy <robin.murphy@arm.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
chris@zankel.net, linux-xtensa@linux-xtensa.org,
keescook@chromium.org, sfr@canb.auug.org.au, tony@atomide.com,
Catalin Marinas <catalin.marinas@arm.com>,
joro@8bytes.org, Will Deacon <will.deacon@arm.com>,
linux@armlinux.org.uk, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, jcmvbkbc@gmail.com,
wsa+renesas@sang-engineering.com, akpm@linux-foundation.org,
treding@nvidia.com, dwmw2@infradead.org, iamjoonsoo.kim@lge.com,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 1/2] dma-contiguous: Abstract dma_{alloc, free}_contiguous()
Date: Thu, 23 May 2019 20:59:30 -0600 [thread overview]
Message-ID: <CALdTtnuwRKkna_y5_5BdEYWNRbOQnLvtfz1PY-d4r78tj5hgVw@mail.gmail.com> (raw)
In-Reply-To: <CALdTtnurdNe4+oJjSJfWw1ONf8-xvJ8KhonQkJNj+4LDZT7jAQ@mail.gmail.com>
On Thu, May 23, 2019 at 7:52 PM dann frazier <dann.frazier@canonical.com> wrote:
>
> On Mon, May 6, 2019 at 4:35 PM Nicolin Chen <nicoleotsuka@gmail.com> 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 <hch@lst.de>
> > Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
> > ---
> > Changelog
> > 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 | 10 +++++++
> > kernel/dma/contiguous.c | 48 ++++++++++++++++++++++++++++++++++
> > kernel/dma/direct.c | 24 +++--------------
> > 3 files changed, 62 insertions(+), 20 deletions(-)
> >
> > diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
> > index f247e8aa5e3d..dacbdcb91a89 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 +159,14 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
> > return false;
> > }
> >
> > +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);
> > }
>
> This breaks the build for me if CONFIG_DMA_CMA=n:
>
> LD [M] fs/9p/9p.o
> ld: fs/9p/vfs_inode.o: in function `dma_alloc_contiguous':
> vfs_inode.c:(.text+0xa60): multiple definition of
> `dma_alloc_contiguous'; fs/9p/vfs_super.o:vfs_super.c:(.text+0x500):
> first defined here
>
> Do the following insertions need to be under an #ifdef CONFIG_DMA_CMA ?
Ah, no - the problem is actually a missing "static inline" in the
!CONFIG_DMA_CMA version of dma_alloc_contiguous().
-dann
> > +/**
> > + * 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
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-05-24 2:59 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-06 22:33 [PATCH v2 0/2] Optimize dma_*_from_contiguous calls Nicolin Chen
2019-05-06 22:33 ` [PATCH v2 1/2] dma-contiguous: Abstract dma_{alloc,free}_contiguous() Nicolin Chen
2019-05-24 1:52 ` [PATCH v2 1/2] dma-contiguous: Abstract dma_{alloc, free}_contiguous() dann frazier
2019-05-24 2:59 ` dann frazier [this message]
2019-05-24 3:49 ` Nicolin Chen
2019-05-06 22:33 ` [PATCH v2 2/2] dma-contiguous: Use fallback alloc_pages for single pages Nicolin Chen
2019-08-23 12:49 ` Masahiro Yamada
2019-08-23 12:56 ` Masahiro Yamada
2019-08-25 1:10 ` Christoph Hellwig
2019-08-26 2:05 ` Masahiro Yamada
2019-08-26 7:33 ` Christoph Hellwig
2019-08-27 7:45 ` Masahiro Yamada
2019-08-27 7:50 ` Christoph Hellwig
2019-08-27 9:03 ` Masahiro Yamada
2019-08-27 11:55 ` Christoph Hellwig
2019-08-28 10:53 ` Masahiro Yamada
2019-08-28 12:23 ` Masahiro Yamada
2019-08-29 11:45 ` Masahiro Yamada
2019-08-23 22:11 ` Nicolin Chen
2019-08-26 1:56 ` Masahiro Yamada
2019-05-08 12:52 ` [PATCH v2 0/2] Optimize dma_*_from_contiguous calls Christoph Hellwig
2019-05-08 18:08 ` Nicolin Chen
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