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

[Andrew F. Davis]

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@xxxxxxxxxx>
> Cc: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
> Cc: Pratik Patel <pratikp@xxxxxxxxxxxxxx>
> Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
> Cc: Vincent Donnefort <Vincent.Donnefort@xxxxxxx>
> Cc: Sudipto Paul <Sudipto.Paul@xxxxxxx>
> Cc: Andrew F. Davis <afd@xxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: Chenbo Feng <fengc@xxxxxxxxxx>
> Cc: Alistair Strachan <astrachan@xxxxxxxxxx>
> Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
> Cc: Sandeep Patil <sspatil@xxxxxxxxxx>
> Cc: Hillf Danton <hdanton@xxxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Reviewed-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> Reviewed-by: Brian Starkey <brian.starkey@xxxxxxx>
> Acked-by: Sandeep Patil <sspatil@xxxxxxxxxxx>
> Acked-by: Laura Abbott <labbott@xxxxxxxxxx>
> Tested-by: Ayan Kumar Halder <ayan.halder@xxxxxxx>
> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> ---
> 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");
>