Re: [RESEND][PATCH v16 3/5] dma-buf: heaps: Add system heap to dmabuf heaps

Andrew F. Davis
2019-12-12T16:21:26Z

On 12/3/19 12:26 PM, John Stultz wrote:
> This patch adds system heap to the dma-buf heaps framework.
>
> This allows applications to get a page-allocator backed dma-buf
> for non-contiguous memory.
>
> This code is an evolution of the Android ION implementation, so
> thanks to its original authors and maintainters:
> Rebecca Schultz Zavin, Colin Cross, Laura Abbott, and others!
>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: Liam Mark <lmark@codeaurora.org>
> Cc: Pratik Patel <pratikp@codeaurora.org>
> Cc: Brian Starkey <Brian.Starkey@arm.com>
> Cc: Vincent Donnefort <Vincent.Donnefort@arm.com>
> Cc: Sudipto Paul <Sudipto.Paul@arm.com>
> Cc: Andrew F. Davis <afd@ti.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Chenbo Feng <fengc@google.com>
> Cc: Alistair Strachan <astrachan@google.com>
> Cc: Hridya Valsaraju <hridya@google.com>
> Cc: Sandeep Patil <sspatil@google.com>
> Cc: Hillf Danton <hdanton@sina.com>
> Cc: Dave Airlie <airlied@gmail.com>
> Cc: dri-devel@lists.freedesktop.org
> Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Reviewed-by: Brian Starkey <brian.starkey@arm.com>
> Acked-by: Sandeep Patil <sspatil@android.com>
> Acked-by: Laura Abbott <labbott@redhat.com>
> Tested-by: Ayan Kumar Halder <ayan.halder@arm.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> v2:
> * Switch allocate to return dmabuf fd
> * Simplify init code
> * Checkpatch fixups
> * Droped dead system-contig code
> v3:
> * Whitespace fixups from Benjamin
> * Make sure we're zeroing the allocated pages (from Liam)
> * Use PAGE_ALIGN() consistently (suggested by Brian)
> * Fold in new registration style from Andrew
> * Avoid needless dynamic allocation of sys_heap (suggested by
> Christoph)
> * Minor cleanups
> * Folded in changes from Andrew to use simplified page list
> from the heap helpers
> v4:
> * Optimization to allocate pages in chunks, similar to old
> pagepool code
> * Use fd_flags when creating dmabuf fd (Suggested by Benjamin)
> v5:
> * Back out large order page allocations (was leaking memory,
> as the page array didn't properly track order size)
> v6:
> * Minor whitespace change suggested by Brian
> * Remove unused variable
> v7:
> * Use newly lower-cased init_heap_helper_buffer helper
> * Add system heap DOS avoidance suggested by Laura from ION code
> * Use new dmabuf export helper
> v8:
> * Make struct dma_heap_ops consts (suggested by Christoph)
> * Get rid of needless struct system_heap (suggested by Christoph)
> * Condense dma_heap_buffer and heap_helper_buffer (suggested by
> Christoph)
> * Add forgotten include file to fix build issue on x86
> v12:
> * Minor tweaks to prep loading heap from module
> v14:
> * Fix "redundant assignment to variable ret" issue reported
> by Colin King and fixed by Andrew Davis
> v15:
> * Drop unused heap flag from heap_helper_buffer as suggested
> by Sandeep Patil
> ---
> drivers/dma-buf/Kconfig | 2 +
> drivers/dma-buf/heaps/Kconfig | 6 ++
> drivers/dma-buf/heaps/Makefile | 1 +
> drivers/dma-buf/heaps/system_heap.c | 123 ++++++++++++++++++++++++++++
> 4 files changed, 132 insertions(+)
> create mode 100644 drivers/dma-buf/heaps/Kconfig
> create mode 100644 drivers/dma-buf/heaps/system_heap.c
>
> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
> index bffa58fc3e6e..0613bb7770f5 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -53,4 +53,6 @@ menuconfig DMABUF_HEAPS
> allows userspace to allocate dma-bufs that can be shared
> between drivers.
>
> +source "drivers/dma-buf/heaps/Kconfig"
> +
> endmenu
> diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
> new file mode 100644
> index 000000000000..205052744169
> --- /dev/null
> +++ b/drivers/dma-buf/heaps/Kconfig
> @@ -0,0 +1,6 @@
> +config DMABUF_HEAPS_SYSTEM
> + bool "DMA-BUF System Heap"
> + depends on DMABUF_HEAPS
> + help
> + Choose this option to enable the system dmabuf heap. The system heap
> + is backed by pages from the buddy allocator. If in doubt, say Y.
> diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
> index de49898112db..d1808eca2581 100644
> --- a/drivers/dma-buf/heaps/Makefile
> +++ b/drivers/dma-buf/heaps/Makefile
> @@ -1,2 +1,3 @@
> # SPDX-License-Identifier: GPL-2.0
> obj-y += heap-helpers.o
> +obj-$(CONFIG_DMABUF_HEAPS_SYSTEM) += system_heap.o
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> new file mode 100644
> index 000000000000..1aa01e98c595
> --- /dev/null
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -0,0 +1,123 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * DMABUF System heap exporter
> + *
> + * Copyright (C) 2011 Google, Inc.
> + * Copyright (C) 2019 Linaro Ltd.
> + */
> +
> +#include <linux/dma-buf.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/dma-heap.h>
> +#include <linux/err.h>
> +#include <linux/highmem.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/scatterlist.h>
> +#include <linux/slab.h>
> +#include <linux/sched/signal.h>
> +#include <asm/page.h>
> +
> +#include "heap-helpers.h"
> +
> +struct dma_heap *sys_heap;
> +
> +static void system_heap_free(struct heap_helper_buffer *buffer)
> +{
> + pgoff_t pg;
> +
> + for (pg = 0; pg < buffer->pagecount; pg++)
> + __free_page(buffer->pages[pg]);
> + kfree(buffer->pages);
> + kfree(buffer);
> +}
> +
> +static int system_heap_allocate(struct dma_heap *heap,
> + unsigned long len,
> + unsigned long fd_flags,
> + unsigned long heap_flags)
> +{
> + struct heap_helper_buffer *helper_buffer;
> + struct dma_buf *dmabuf;
> + int ret = -ENOMEM;
> + pgoff_t pg;
> +
> + helper_buffer = kzalloc(sizeof(*helper_buffer), GFP_KERNEL);
> + if (!helper_buffer)
> + return -ENOMEM;
> +
> + init_heap_helper_buffer(helper_buffer, system_heap_free);
> + helper_buffer->heap = heap;
> + helper_buffer->size = len;
> +
> + helper_buffer->pagecount = len / PAGE_SIZE;
> + helper_buffer->pages = kmalloc_array(helper_buffer->pagecount,
> + sizeof(*helper_buffer->pages),
> + GFP_KERNEL);
> + if (!helper_buffer->pages) {
> + ret = -ENOMEM;
> + goto err0;
> + }
> +
> + for (pg = 0; pg < helper_buffer->pagecount; pg++) {
> + /*
> + * Avoid trying to allocate memory if the process
> + * has been killed by by SIGKILL
> + */
> + if (fatal_signal_pending(current))
> + goto err1;
> +
> + helper_buffer->pages[pg] = alloc_page(GFP_KERNEL | __GFP_ZERO);
> + if (!helper_buffer->pages[pg])
> + goto err1;
> + }
> +
> + /* create the dmabuf */
> + dmabuf = heap_helper_export_dmabuf(helper_buffer, fd_flags);
> + if (IS_ERR(dmabuf)) {
> + ret = PTR_ERR(dmabuf);
> + goto err1;
> + }
> +
> + helper_buffer->dmabuf = dmabuf;
> +
> + ret = dma_buf_fd(dmabuf, fd_flags);
> + if (ret < 0) {
> + dma_buf_put(dmabuf);
> + /* just return, as put will call release and that will free */
> + return ret;
> + }
> +
> + return ret;
> +
> +err1:
> + while (pg > 0)
> + __free_page(helper_buffer->pages[--pg]);
> + kfree(helper_buffer->pages);
> +err0:
> + kfree(helper_buffer);
> +
> + return ret;
> +}
> +
> +static const struct dma_heap_ops system_heap_ops = {
> + .allocate = system_heap_allocate,
> +};
> +
> +static int system_heap_create(void)
> +{
> + struct dma_heap_export_info exp_info;
> + int ret = 0;
> +
> + exp_info.name = "system_heap";

nit: Would prefer the name just be "system", the heap part is redundant
given it will be in a "heaps" directory, other heaps don't have that. As
the heap will be accessed by users using this name:
(/sys/dma_heap/system_heap) we need to think of it like an ABI and get
it right the first time. The directory name should probably also be
plural "heaps" as it is a collection of heaps..

Andrew

> + exp_info.ops = &system_heap_ops;
> + exp_info.priv = NULL;
> +
> + sys_heap = dma_heap_add(&exp_info);
> + if (IS_ERR(sys_heap))
> + ret = PTR_ERR(sys_heap);
> +
> + return ret;
> +}
> +module_init(system_heap_create);
> +MODULE_LICENSE("GPL v2");
>