On 5/13/25 11:28, wangtao wrote:
> Support direct file I/O operations for system_heap dma-buf objects.
> Implementation includes:
> 1. Convert sg_table to bio_vec
That is usually illegal for DMA-bufs.
Regards,
Christian.
> 2. Set IOCB_DIRECT when O_DIRECT is supported
> 3. Invoke vfs_iocb_iter_read()/vfs_iocb_iter_write() for actual I/O
>
> Performance metrics (UFS 4.0 device @4GB/s, Arm64 CPU @1GHz):
>
> | Metric | 1MB | 8MB | 64MB | 1024MB | 3072MB |
> |--------------------|-------:|-------:|--------:|---------:|---------:|
> | Buffer Read (us) | 1658 | 9028 | 69295 | 1019783 | 2978179 |
> | Direct Read (us) | 707 | 2647 | 18689 | 299627 | 937758 |
> | Buffer Rate (MB/s) | 603 | 886 | 924 | 1004 | 1032 |
> | Direct Rate (MB/s) | 1414 | 3022 | 3425 | 3418 | 3276 |
>
> Signed-off-by: wangtao <tao.wang...@honor.com>
> ---
> drivers/dma-buf/heaps/system_heap.c | 118 ++++++++++++++++++++++++++++
> 1 file changed, 118 insertions(+)
>
> diff --git a/drivers/dma-buf/heaps/system_heap.c
> b/drivers/dma-buf/heaps/system_heap.c
> index 26d5dc89ea16..f7b71b9843aa 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -20,6 +20,8 @@
> #include <linux/scatterlist.h>
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> +#include <linux/bvec.h>
> +#include <linux/uio.h>
>
> static struct dma_heap *sys_heap;
>
> @@ -281,6 +283,121 @@ static void system_heap_vunmap(struct dma_buf *dmabuf,
> struct iosys_map *map)
> iosys_map_clear(map);
> }
>
> +static struct bio_vec *system_heap_init_bvec(struct system_heap_buffer
> *buffer,
> + size_t offset, size_t len, int *nr_segs)
> +{
> + struct sg_table *sgt = &buffer->sg_table;
> + struct scatterlist *sg;
> + size_t length = 0;
> + unsigned int i, k = 0;
> + struct bio_vec *bvec;
> + size_t sg_left;
> + size_t sg_offset;
> + size_t sg_len;
> +
> + bvec = kvcalloc(sgt->nents, sizeof(*bvec), GFP_KERNEL);
> + if (!bvec)
> + return NULL;
> +
> + for_each_sg(sgt->sgl, sg, sgt->nents, i) {
> + length += sg->length;
> + if (length <= offset)
> + continue;
> +
> + sg_left = length - offset;
> + sg_offset = sg->offset + sg->length - sg_left;
> + sg_len = min(sg_left, len);
> +
> + bvec[k].bv_page = sg_page(sg);
> + bvec[k].bv_len = sg_len;
> + bvec[k].bv_offset = sg_offset;
> + k++;
> +
> + offset += sg_len;
> + len -= sg_len;
> + if (len <= 0)
> + break;
> + }
> +
> + *nr_segs = k;
> + return bvec;
> +}
> +
> +static int system_heap_rw_file(struct system_heap_buffer *buffer, bool
> is_read,
> + bool direct_io, struct file *filp, loff_t file_offset,
> + size_t buf_offset, size_t len)
> +{
> + struct bio_vec *bvec;
> + int nr_segs = 0;
> + struct iov_iter iter;
> + struct kiocb kiocb;
> + ssize_t ret = 0;
> +
> + if (direct_io) {
> + if (!(filp->f_mode & FMODE_CAN_ODIRECT))
> + return -EINVAL;
> + }
> +
> + bvec = system_heap_init_bvec(buffer, buf_offset, len, &nr_segs);
> + if (!bvec)
> + return -ENOMEM;
> +
> + iov_iter_bvec(&iter, is_read ? ITER_DEST : ITER_SOURCE, bvec, nr_segs,
> len);
> + init_sync_kiocb(&kiocb, filp);
> + kiocb.ki_pos = file_offset;
> + if (direct_io)
> + kiocb.ki_flags |= IOCB_DIRECT;
> +
> + while (kiocb.ki_pos < file_offset + len) {
> + if (is_read)
> + ret = vfs_iocb_iter_read(filp, &kiocb, &iter);
> + else
> + ret = vfs_iocb_iter_write(filp, &kiocb, &iter);
> + if (ret <= 0)
> + break;
> + }
> +
> + kvfree(bvec);
> + return ret < 0 ? ret : 0;
> +}
> +
> +static int system_heap_dma_buf_rw_file(struct dma_buf *dmabuf,
> + struct dma_buf_rw_file *back)
> +{
> + struct system_heap_buffer *buffer = dmabuf->priv;
> + int ret = 0;
> + __u32 op = back->flags & DMA_BUF_RW_FLAGS_OP_MASK;
> + bool direct_io = back->flags & DMA_BUF_RW_FLAGS_DIRECT;
> + struct file *filp;
> +
> + if (op != DMA_BUF_RW_FLAGS_READ && op != DMA_BUF_RW_FLAGS_WRITE)
> + return -EINVAL;
> + if (direct_io) {
> + if (!PAGE_ALIGNED(back->file_offset) ||
> + !PAGE_ALIGNED(back->buf_offset) ||
> + !PAGE_ALIGNED(back->buf_len))
> + return -EINVAL;
> + }
> + if (!back->buf_len || back->buf_len > dmabuf->size ||
> + back->buf_offset >= dmabuf->size ||
> + back->buf_offset + back->buf_len > dmabuf->size)
> + return -EINVAL;
> + if (back->file_offset + back->buf_len < back->file_offset)
> + return -EINVAL;
> +
> + filp = fget(back->fd);
> + if (!filp)
> + return -EBADF;
> +
> + mutex_lock(&buffer->lock);
> + ret = system_heap_rw_file(buffer, op == DMA_BUF_RW_FLAGS_READ,
> direct_io,
> + filp, back->file_offset, back->buf_offset,
> back->buf_len);
> + mutex_unlock(&buffer->lock);
> +
> + fput(filp);
> + return ret;
> +}
> +
> static void system_heap_dma_buf_release(struct dma_buf *dmabuf)
> {
> struct system_heap_buffer *buffer = dmabuf->priv;
> @@ -308,6 +425,7 @@ static const struct dma_buf_ops system_heap_buf_ops = {
> .mmap = system_heap_mmap,
> .vmap = system_heap_vmap,
> .vunmap = system_heap_vunmap,
> + .rw_file = system_heap_dma_buf_rw_file,
> .release = system_heap_dma_buf_release,
> };
>
