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    SubjectRe: [PATCH v3 1/2] dma-contiguous: Abstract dma_{alloc,free}_contiguous()
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    On Thu, 2019-07-25 at 09:50 -0700, Nicolin Chen wrote:
    > 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
    >

    Hi,
    I compiled vivid as built-in into the kernel (not as a separate module) for nitrogen8m device (imx8) and
    set it to use contig dma for mem_ops by adding the kernel param
    vivid.allocators=1,1,...

    I use this devicetree patch for the dtb file: https://lkml.org/lkml/2019/7/24/789. Although it should
    be the same on any Aarch64 platform.

    Then, on the board I run the command:

    v4l2-ctl -d3 -v width=2592,height=1944,pixelformat=UYVY,bytesperline=5184 --stream-mmap --stream-to video.UYVY

    In every run there is a different crash. Here is one of them: https://pastebin.com/xXgbXMAN

    Dafna
    > >
    > >
    > > > > On Fri, 24 May 2019 at 01:08, 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
    > > > 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
    > > >

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