Re: [RFC][PATCH 2/5 v2] dma-buf: heaps: Add heap helpers

[Andrew F. Davis]

On 3/5/19 2:54 PM, John Stultz wrote:
> Add generic helper dmabuf ops for dma heaps, so we can reduce
> the amount of duplicative code for the exported dmabufs.
> 
> 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: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
> Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
> Cc: Andrew F. Davis <afd@xxxxxx>
> Cc: Chenbo Feng <fengc@xxxxxxxxxx>
> Cc: Alistair Strachan <astrachan@xxxxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> ---
> v2:
> * Removed cache management performance hack that I had
>   accidentally folded in.
> * Removed stats code that was in helpers
> * Lots of checkpatch cleanups
> ---
>  drivers/dma-buf/Makefile             |   1 +
>  drivers/dma-buf/heaps/Makefile       |   2 +
>  drivers/dma-buf/heaps/heap-helpers.c | 335 +++++++++++++++++++++++++++++++++++
>  drivers/dma-buf/heaps/heap-helpers.h |  48 +++++
>  4 files changed, 386 insertions(+)
>  create mode 100644 drivers/dma-buf/heaps/Makefile
>  create mode 100644 drivers/dma-buf/heaps/heap-helpers.c
>  create mode 100644 drivers/dma-buf/heaps/heap-helpers.h
> 
> diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
> index b0332f1..09c2f2d 100644
> --- a/drivers/dma-buf/Makefile
> +++ b/drivers/dma-buf/Makefile
> @@ -1,4 +1,5 @@
>  obj-y := dma-buf.o dma-fence.o dma-fence-array.o reservation.o seqno-fence.o
> +obj-$(CONFIG_DMABUF_HEAPS)	+= heaps/
>  obj-$(CONFIG_DMABUF_HEAPS)	+= dma-heap.o
>  obj-$(CONFIG_SYNC_FILE)		+= sync_file.o
>  obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o
> diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
> new file mode 100644
> index 0000000..de49898
> --- /dev/null
> +++ b/drivers/dma-buf/heaps/Makefile
> @@ -0,0 +1,2 @@
> +# SPDX-License-Identifier: GPL-2.0
> +obj-y					+= heap-helpers.o
> diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c
> new file mode 100644
> index 0000000..ae5e9d0
> --- /dev/null
> +++ b/drivers/dma-buf/heaps/heap-helpers.c
> @@ -0,0 +1,335 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/device.h>
> +#include <linux/dma-buf.h>
> +#include <linux/err.h>
> +#include <linux/idr.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +#include <uapi/linux/dma-heap.h>
> +
> +#include "heap-helpers.h"
> +
> +
> +static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer)
> +{
> +	struct scatterlist *sg;
> +	int i, j;
> +	void *vaddr;
> +	pgprot_t pgprot;
> +	struct sg_table *table = buffer->sg_table;
> +	int npages = PAGE_ALIGN(buffer->heap_buffer.size) / PAGE_SIZE;
> +	struct page **pages = vmalloc(array_size(npages,
> +						 sizeof(struct page *)));
> +	struct page **tmp = pages;
> +
> +	if (!pages)
> +		return ERR_PTR(-ENOMEM);
> +
> +	pgprot = PAGE_KERNEL;
> +
> +	for_each_sg(table->sgl, sg, table->nents, i) {
> +		int npages_this_entry = PAGE_ALIGN(sg->length) / PAGE_SIZE;
> +		struct page *page = sg_page(sg);
> +
> +		WARN_ON(i >= npages);
> +		for (j = 0; j < npages_this_entry; j++)
> +			*(tmp++) = page++;
> +	}
> +	vaddr = vmap(pages, npages, VM_MAP, pgprot);
> +	vfree(pages);
> +
> +	if (!vaddr)
> +		return ERR_PTR(-ENOMEM);
> +
> +	return vaddr;
> +}
> +
> +static int dma_heap_map_user(struct heap_helper_buffer *buffer,
> +			 struct vm_area_struct *vma)
> +{
> +	struct sg_table *table = buffer->sg_table;
> +	unsigned long addr = vma->vm_start;
> +	unsigned long offset = vma->vm_pgoff * PAGE_SIZE;
> +	struct scatterlist *sg;
> +	int i;
> +	int ret;
> +
> +	for_each_sg(table->sgl, sg, table->nents, i) {
> +		struct page *page = sg_page(sg);
> +		unsigned long remainder = vma->vm_end - addr;
> +		unsigned long len = sg->length;
> +
> +		if (offset >= sg->length) {
> +			offset -= sg->length;
> +			continue;
> +		} else if (offset) {
> +			page += offset / PAGE_SIZE;
> +			len = sg->length - offset;
> +			offset = 0;
> +		}
> +		len = min(len, remainder);
> +		ret = remap_pfn_range(vma, addr, page_to_pfn(page), len,
> +				      vma->vm_page_prot);
> +		if (ret)
> +			return ret;
> +		addr += len;
> +		if (addr >= vma->vm_end)
> +			return 0;
> +	}
> +
> +	return 0;
> +}
> +
> +
> +void dma_heap_buffer_destroy(struct dma_heap_buffer *heap_buffer)
> +{
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +
> +	if (buffer->kmap_cnt > 0) {
> +		pr_warn_once("%s: buffer still mapped in the kernel\n",
> +			     __func__);
> +		vunmap(buffer->vaddr);
> +	}
> +
> +	buffer->free(buffer);
> +}
> +
> +static void *dma_heap_buffer_kmap_get(struct dma_heap_buffer *heap_buffer)
> +{
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +	void *vaddr;
> +
> +	if (buffer->kmap_cnt) {
> +		buffer->kmap_cnt++;
> +		return buffer->vaddr;
> +	}
> +	vaddr = dma_heap_map_kernel(buffer);

The function is called "kmap" but here we go and vmap the whole buffer.
The function names are not consistent here.

> +	if (WARN_ONCE(!vaddr,
> +		      "heap->ops->map_kernel should return ERR_PTR on error"))
> +		return ERR_PTR(-EINVAL);
> +	if (IS_ERR(vaddr))
> +		return vaddr;
> +	buffer->vaddr = vaddr;
> +	buffer->kmap_cnt++;
> +	return vaddr;
> +}
> +
> +static void dma_heap_buffer_kmap_put(struct dma_heap_buffer *heap_buffer)
> +{
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +
> +	buffer->kmap_cnt--;
> +	if (!buffer->kmap_cnt) {
> +		vunmap(buffer->vaddr);
> +		buffer->vaddr = NULL;
> +	}
> +}
> +
> +static struct sg_table *dup_sg_table(struct sg_table *table)
> +{
> +	struct sg_table *new_table;
> +	int ret, i;
> +	struct scatterlist *sg, *new_sg;
> +
> +	new_table = kzalloc(sizeof(*new_table), GFP_KERNEL);
> +	if (!new_table)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = sg_alloc_table(new_table, table->nents, GFP_KERNEL);
> +	if (ret) {
> +		kfree(new_table);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	new_sg = new_table->sgl;
> +	for_each_sg(table->sgl, sg, table->nents, i) {
> +		memcpy(new_sg, sg, sizeof(*sg));
> +		new_sg->dma_address = 0;
> +		new_sg = sg_next(new_sg);
> +	}
> +
> +	return new_table;
> +}
> +
> +static void free_duped_table(struct sg_table *table)
> +{
> +	sg_free_table(table);
> +	kfree(table);
> +}
> +
> +struct dma_heaps_attachment {
> +	struct device *dev;
> +	struct sg_table *table;
> +	struct list_head list;
> +};
> +
> +static int dma_heap_attach(struct dma_buf *dmabuf,
> +			      struct dma_buf_attachment *attachment)
> +{
> +	struct dma_heaps_attachment *a;
> +	struct sg_table *table;
> +	struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +
> +	a = kzalloc(sizeof(*a), GFP_KERNEL);
> +	if (!a)
> +		return -ENOMEM;
> +
> +	table = dup_sg_table(buffer->sg_table);
> +	if (IS_ERR(table)) {
> +		kfree(a);
> +		return -ENOMEM;
> +	}
> +
> +	a->table = table;
> +	a->dev = attachment->dev;
> +	INIT_LIST_HEAD(&a->list);
> +
> +	attachment->priv = a;
> +
> +	mutex_lock(&buffer->lock);
> +	list_add(&a->list, &buffer->attachments);
> +	mutex_unlock(&buffer->lock);
> +
> +	return 0;
> +}
> +
> +static void dma_heap_detatch(struct dma_buf *dmabuf,
> +				struct dma_buf_attachment *attachment)
> +{
> +	struct dma_heaps_attachment *a = attachment->priv;
> +	struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +
> +	mutex_lock(&buffer->lock);
> +	list_del(&a->list);
> +	mutex_unlock(&buffer->lock);
> +	free_duped_table(a->table);
> +
> +	kfree(a);
> +}
> +
> +static struct sg_table *dma_heap_map_dma_buf(
> +					struct dma_buf_attachment *attachment,
> +					enum dma_data_direction direction)
> +{
> +	struct dma_heaps_attachment *a = attachment->priv;
> +	struct sg_table *table;
> +
> +	table = a->table;
> +
> +	if (!dma_map_sg(attachment->dev, table->sgl, table->nents,
> +			direction))
> +		table = ERR_PTR(-ENOMEM);
> +	return table;
> +}
> +
> +static void dma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
> +			      struct sg_table *table,
> +			      enum dma_data_direction direction)
> +{
> +	dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction);
> +}
> +
> +static int dma_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
> +{
> +	struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +	int ret = 0;
> +
> +	mutex_lock(&buffer->lock);
> +	/* now map it to userspace */
> +	ret = dma_heap_map_user(buffer, vma);

Only used here, we can just put is functions code here. Also do we need
this locked? What can race here? Everything accessed is static for the
buffers lifetime.

> +	mutex_unlock(&buffer->lock);
> +
> +	if (ret)
> +		pr_err("%s: failure mapping buffer to userspace\n",
> +		       __func__);
> +
> +	return ret;
> +}
> +
> +static void dma_heap_dma_buf_release(struct dma_buf *dmabuf)
> +{
> +	struct dma_heap_buffer *buffer = dmabuf->priv;
> +
> +	dma_heap_buffer_destroy(buffer);
> +}
> +
> +static void *dma_heap_dma_buf_kmap(struct dma_buf *dmabuf,
> +					unsigned long offset)
> +{
> +	struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +
> +	return buffer->vaddr + offset * PAGE_SIZE;
> +}
> +
> +static void dma_heap_dma_buf_kunmap(struct dma_buf *dmabuf,
> +					unsigned long offset,
> +					void *ptr)
> +{
> +}
> +
> +static int dma_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
> +					enum dma_data_direction direction)
> +{
> +	struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +	void *vaddr;
> +	struct dma_heaps_attachment *a;
> +	int ret = 0;
> +
> +	mutex_lock(&buffer->lock);
> +	vaddr = dma_heap_buffer_kmap_get(heap_buffer);


Not needed here, this can be dropped and so can the
dma_heap_buffer_kmap_put() below.

Andrew

> +	if (IS_ERR(vaddr)) {
> +		ret = PTR_ERR(vaddr);
> +		goto unlock;
> +	}
> +	mutex_unlock(&buffer->lock);
> +
> +	mutex_lock(&buffer->lock);
> +	list_for_each_entry(a, &buffer->attachments, list) {
> +		dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents,
> +				    direction);
> +	}
> +
> +unlock:
> +	mutex_unlock(&buffer->lock);
> +	return ret;
> +}
> +
> +static int dma_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
> +				      enum dma_data_direction direction)
> +{
> +	struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> +	struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> +	struct dma_heaps_attachment *a;
> +
> +	mutex_lock(&buffer->lock);
> +	dma_heap_buffer_kmap_put(heap_buffer);
> +	mutex_unlock(&buffer->lock);
> +
> +	mutex_lock(&buffer->lock);
> +	list_for_each_entry(a, &buffer->attachments, list) {
> +		dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents,
> +				       direction);
> +	}
> +	mutex_unlock(&buffer->lock);
> +
> +	return 0;
> +}
> +
> +const struct dma_buf_ops heap_helper_ops = {
> +	.map_dma_buf = dma_heap_map_dma_buf,
> +	.unmap_dma_buf = dma_heap_unmap_dma_buf,
> +	.mmap = dma_heap_mmap,
> +	.release = dma_heap_dma_buf_release,
> +	.attach = dma_heap_attach,
> +	.detach = dma_heap_detatch,
> +	.begin_cpu_access = dma_heap_dma_buf_begin_cpu_access,
> +	.end_cpu_access = dma_heap_dma_buf_end_cpu_access,
> +	.map = dma_heap_dma_buf_kmap,
> +	.unmap = dma_heap_dma_buf_kunmap,
> +};
> diff --git a/drivers/dma-buf/heaps/heap-helpers.h b/drivers/dma-buf/heaps/heap-helpers.h
> new file mode 100644
> index 0000000..0bd8643
> --- /dev/null
> +++ b/drivers/dma-buf/heaps/heap-helpers.h
> @@ -0,0 +1,48 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * DMABUF Heaps helper code
> + *
> + * Copyright (C) 2011 Google, Inc.
> + * Copyright (C) 2019 Linaro Ltd.
> + */
> +
> +#ifndef _HEAP_HELPERS_H
> +#define _HEAP_HELPERS_H
> +
> +#include <linux/dma-heap.h>
> +#include <linux/list.h>
> +
> +struct heap_helper_buffer {
> +	struct dma_heap_buffer heap_buffer;
> +
> +	unsigned long private_flags;
> +	void *priv_virt;
> +	struct mutex lock;
> +	int kmap_cnt;
> +	void *vaddr;
> +	struct sg_table *sg_table;
> +	struct list_head attachments;
> +
> +	void (*free)(struct heap_helper_buffer *buffer);
> +
> +};
> +
> +#define to_helper_buffer(x) \
> +	container_of(x, struct heap_helper_buffer, heap_buffer)
> +
> +static inline void INIT_HEAP_HELPER_BUFFER(struct heap_helper_buffer *buffer,
> +				 void (*free)(struct heap_helper_buffer *))
> +{
> +	buffer->private_flags = 0;
> +	buffer->priv_virt = NULL;
> +	mutex_init(&buffer->lock);
> +	buffer->kmap_cnt = 0;
> +	buffer->vaddr = NULL;
> +	buffer->sg_table = NULL;
> +	INIT_LIST_HEAD(&buffer->attachments);
> +	buffer->free = free;
> +}
> +
> +extern const struct dma_buf_ops heap_helper_ops;
> +
> +#endif /* _HEAP_HELPERS_H */
>