Message-ID: <63189ac3-7725-4ad7-966a-4ca679a25d12@amd.com>
Date: Thu, 11 Jul 2024 13:39:05 +0200
From: Christian König <christian.koenig@....com>
To: Huan Yang <link@...o.com>, Sumit Semwal <sumit.semwal@...aro.org>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
 "T.J. Mercier" <tjmercier@...gle.com>, linux-media@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
 linux-kernel@...r.kernel.org
Cc: opensource.kernel@...o.com
Subject: Re: [PATCH 1/2] dma-buf: heaps: DMA_HEAP_IOCTL_ALLOC_READ_FILE
 framework

Am 11.07.24 um 11:18 schrieb Huan Yang:
> Hi Christian,
>
> Thanks for your reply.
>
> 在 2024/7/11 17:00, Christian König 写道:
>> Am 11.07.24 um 09:42 schrieb Huan Yang:
>>> Some user may need load file into dma-buf, current
>>> way is:
>>>    1. allocate a dma-buf, get dma-buf fd
>>>    2. mmap dma-buf fd into vaddr
>>>    3. read(file_fd, vaddr, fsz)
>>> This is too heavy if fsz reached to GB.
>>
>> You need to describe a bit more why that is to heavy. I can only 
>> assume you need to save memory bandwidth and avoid the extra copy 
>> with the CPU.
>
> Sorry for the oversimplified explanation. But, yes, you're right, we 
> want to avoid this.
>
> As we are dealing with embedded devices, the available memory and 
> computing power for users are usually limited.(The maximum available 
> memory is currently
>
> 24GB, typically ranging from 8-12GB. )
>
> Also, the CPU computing power is also usually in short supply, due to 
> limited battery capacity and limited heat dissipation capabilities.
>
> So, we hope to avoid ineffective paths as much as possible.
>
>>
>>> This patch implement a feature called DMA_HEAP_IOCTL_ALLOC_READ_FILE.
>>> User need to offer a file_fd which you want to load into dma-buf, then,
>>> it promise if you got a dma-buf fd, it will contains the file content.
>>
>> Interesting idea, that has at least more potential than trying to 
>> enable direct I/O on mmap()ed DMA-bufs.
>>
>> The approach with the new IOCTL might not work because it is a very 
>> specialized use case.
>
> Thank you for your advice. maybe the "read file" behavior can be 
> attached to an existing allocation?

The point is there are already system calls to do something like that.

See copy_file_range() 
(https://man7.org/linux/man-pages/man2/copy_file_range.2.html) and 
send_file() (https://man7.org/linux/man-pages/man2/sendfile.2.html).

What we probably could do is to internally optimize those.

> I am currently creating a new ioctl to remind the user that memory is 
> being allocated and read, and I am also unsure
>
> whether it is appropriate to add additional parameters to the existing 
> allocate behavior.
>
> Please, give me more suggestion. Thanks.
>
>>
>> But IIRC there was a copy_file_range callback in the file_operations 
>> structure you could use for that. I'm just not sure when and how 
>> that's used with the copy_file_range() system call.
>
> Sorry, I'm not familiar with this, but I will look into it. However, 
> this type of callback function is not currently implemented when 
> exporting
>
> the dma_buf file, which means that I need to implement the callback 
> for it?

If I'm not completely mistaken the copy_file_range, splice_read and 
splice_write callbacks on the struct file_operations 
(https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/fs.h#L1999).

Can be used to implement what you want to do.

Regards,
Christian.

>
>>
>> Regards,
>> Christian.
>>
>>>
>>> Notice, file_fd depends on user how to open this file. So, both buffer
>>> I/O and Direct I/O is supported.
>>>
>>> Signed-off-by: Huan Yang <link@...o.com>
>>> ---
>>>   drivers/dma-buf/dma-heap.c    | 525 
>>> +++++++++++++++++++++++++++++++++-
>>>   include/linux/dma-heap.h      |  57 +++-
>>>   include/uapi/linux/dma-heap.h |  32 +++
>>>   3 files changed, 611 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
>>> index 2298ca5e112e..abe17281adb8 100644
>>> --- a/drivers/dma-buf/dma-heap.c
>>> +++ b/drivers/dma-buf/dma-heap.c
>>> @@ -15,9 +15,11 @@
>>>   #include <linux/list.h>
>>>   #include <linux/slab.h>
>>>   #include <linux/nospec.h>
>>> +#include <linux/highmem.h>
>>>   #include <linux/uaccess.h>
>>>   #include <linux/syscalls.h>
>>>   #include <linux/dma-heap.h>
>>> +#include <linux/vmalloc.h>
>>>   #include <uapi/linux/dma-heap.h>
>>>     #define DEVNAME "dma_heap"
>>> @@ -43,12 +45,462 @@ struct dma_heap {
>>>       struct cdev heap_cdev;
>>>   };
>>>   +/**
>>> + * struct dma_heap_file - wrap the file, read task for dma_heap 
>>> allocate use.
>>> + * @file:        file to read from.
>>> + *
>>> + * @cred:        kthread use, user cred copy to use for the read.
>>> + *
>>> + * @max_batch:        maximum batch size to read, if collect match 
>>> batch,
>>> + *            trigger read, default 128MB, must below file size.
>>> + *
>>> + * @fsz:        file size.
>>> + *
>>> + * @direct:        use direct IO?
>>> + */
>>> +struct dma_heap_file {
>>> +    struct file *file;
>>> +    struct cred *cred;
>>> +    size_t max_batch;
>>> +    size_t fsz;
>>> +    bool direct;
>>> +};
>>> +
>>> +/**
>>> + * struct dma_heap_file_work - represents a dma_heap file read real 
>>> work.
>>> + * @vaddr:        contigous virtual address alloc by vmap, file 
>>> read need.
>>> + *
>>> + * @start_size:        file read start offset, same to 
>>> @dma_heap_file_task->roffset.
>>> + *
>>> + * @need_size:        file read need size, same to 
>>> @dma_heap_file_task->rsize.
>>> + *
>>> + * @heap_file:        file wrapper.
>>> + *
>>> + * @list:        child node of @dma_heap_file_control->works.
>>> + *
>>> + * @refp:        same @dma_heap_file_task->ref, if end of read, put 
>>> ref.
>>> + *
>>> + * @failp:        if any work io failed, set it true, pointp 
>>> @dma_heap_file_task->fail.
>>> + */
>>> +struct dma_heap_file_work {
>>> +    void *vaddr;
>>> +    ssize_t start_size;
>>> +    ssize_t need_size;
>>> +    struct dma_heap_file *heap_file;
>>> +    struct list_head list;
>>> +    atomic_t *refp;
>>> +    bool *failp;
>>> +};
>>> +
>>> +/**
>>> + * struct dma_heap_file_task - represents a dma_heap file read process
>>> + * @ref:        current file work counter, if zero, allocate and read
>>> + *            done.
>>> + *
>>> + * @roffset:        last read offset, current prepared work' begin 
>>> file
>>> + *            start offset.
>>> + *
>>> + * @rsize:        current allocated page size use to read, if reach 
>>> rbatch,
>>> + *            trigger commit.
>>> + *
>>> + * @rbatch:        current prepared work's batch, below 
>>> @dma_heap_file's
>>> + *            batch.
>>> + *
>>> + * @heap_file:        current dma_heap_file
>>> + *
>>> + * @parray:        used for vmap, size is @dma_heap_file's batch's 
>>> number
>>> + *            pages.(this is maximum). Due to single thread file read,
>>> + *            one page array reuse each work prepare is OK.
>>> + *            Each index in parray is PAGE_SIZE.(vmap need)
>>> + *
>>> + * @pindex:        current allocated page filled in @parray's index.
>>> + *
>>> + * @fail:        any work failed when file read?
>>> + *
>>> + * dma_heap_file_task is the production of file read, will prepare 
>>> each work
>>> + * during allocate dma_buf pages, if match current batch, then 
>>> trigger commit
>>> + * and prepare next work. After all batch queued, user going on 
>>> prepare dma_buf
>>> + * and so on, but before return dma_buf fd, need to wait file read 
>>> end and
>>> + * check read result.
>>> + */
>>> +struct dma_heap_file_task {
>>> +    atomic_t ref;
>>> +    size_t roffset;
>>> +    size_t rsize;
>>> +    size_t rbatch;
>>> +    struct dma_heap_file *heap_file;
>>> +    struct page **parray;
>>> +    unsigned int pindex;
>>> +    bool fail;
>>> +};
>>> +
>>> +/**
>>> + * struct dma_heap_file_control - global control of dma_heap file 
>>> read.
>>> + * @works:        @dma_heap_file_work's list head.
>>> + *
>>> + * @lock:        only lock for @works.
>>> + *
>>> + * @threadwq:        wait queue for @work_thread, if commit work, 
>>> @work_thread
>>> + *            wakeup and read this work's file contains.
>>> + *
>>> + * @workwq:        used for main thread wait for file read end, if 
>>> allocation
>>> + *            end before file read. @dma_heap_file_task ref effect 
>>> this.
>>> + *
>>> + * @work_thread:    file read kthread. the dma_heap_file_task 
>>> work's consumer.
>>> + *
>>> + * @heap_fwork_cachep:    @dma_heap_file_work's cachep, it's 
>>> alloc/free frequently.
>>> + *
>>> + * @nr_work:        global number of how many work committed.
>>> + */
>>> +struct dma_heap_file_control {
>>> +    struct list_head works;
>>> +    spinlock_t lock;
>>> +    wait_queue_head_t threadwq;
>>> +    wait_queue_head_t workwq;
>>> +    struct task_struct *work_thread;
>>> +    struct kmem_cache *heap_fwork_cachep;
>>> +    atomic_t nr_work;
>>> +};
>>> +
>>> +static struct dma_heap_file_control *heap_fctl;
>>>   static LIST_HEAD(heap_list);
>>>   static DEFINE_MUTEX(heap_list_lock);
>>>   static dev_t dma_heap_devt;
>>>   static struct class *dma_heap_class;
>>>   static DEFINE_XARRAY_ALLOC(dma_heap_minors);
>>>   +/**
>>> + * map_pages_to_vaddr - map each scatter page into contiguous 
>>> virtual address.
>>> + * @heap_ftask:        prepared and need to commit's work.
>>> + *
>>> + * Cached pages need to trigger file read, this function map each 
>>> scatter page
>>> + * into contiguous virtual address, so that file read can easy use.
>>> + * Now that we get vaddr page, cached pages can return to original 
>>> user, so we
>>> + * will not effect dma-buf export even if file read not end.
>>> + */
>>> +static void *map_pages_to_vaddr(struct dma_heap_file_task *heap_ftask)
>>> +{
>>> +    return vmap(heap_ftask->parray, heap_ftask->pindex, VM_MAP,
>>> +            PAGE_KERNEL);
>>> +}
>>> +
>>> +bool dma_heap_prepare_file_read(struct dma_heap_file_task *heap_ftask,
>>> +                struct page *page)
>>> +{
>>> +    struct page **array = heap_ftask->parray;
>>> +    int index = heap_ftask->pindex;
>>> +    int num = compound_nr(page), i;
>>> +    unsigned long sz = page_size(page);
>>> +
>>> +    heap_ftask->rsize += sz;
>>> +    for (i = 0; i < num; ++i)
>>> +        array[index++] = &page[i];
>>> +    heap_ftask->pindex = index;
>>> +
>>> +    return heap_ftask->rsize >= heap_ftask->rbatch;
>>> +}
>>> +
>>> +static struct dma_heap_file_work *
>>> +init_file_work(struct dma_heap_file_task *heap_ftask)
>>> +{
>>> +    struct dma_heap_file_work *heap_fwork;
>>> +    struct dma_heap_file *heap_file = heap_ftask->heap_file;
>>> +
>>> +    if (READ_ONCE(heap_ftask->fail))
>>> +        return NULL;
>>> +
>>> +    heap_fwork = kmem_cache_alloc(heap_fctl->heap_fwork_cachep, 
>>> GFP_KERNEL);
>>> +    if (unlikely(!heap_fwork))
>>> +        return NULL;
>>> +
>>> +    heap_fwork->vaddr = map_pages_to_vaddr(heap_ftask);
>>> +    if (unlikely(!heap_fwork->vaddr)) {
>>> +        kmem_cache_free(heap_fctl->heap_fwork_cachep, heap_fwork);
>>> +        return NULL;
>>> +    }
>>> +
>>> +    heap_fwork->heap_file = heap_file;
>>> +    heap_fwork->start_size = heap_ftask->roffset;
>>> +    heap_fwork->need_size = heap_ftask->rsize;
>>> +    heap_fwork->refp = &heap_ftask->ref;
>>> +    heap_fwork->failp = &heap_ftask->fail;
>>> +    atomic_inc(&heap_ftask->ref);
>>> +    return heap_fwork;
>>> +}
>>> +
>>> +static void destroy_file_work(struct dma_heap_file_work *heap_fwork)
>>> +{
>>> +    vunmap(heap_fwork->vaddr);
>>> +    atomic_dec(heap_fwork->refp);
>>> +    wake_up(&heap_fctl->workwq);
>>> +
>>> +    kmem_cache_free(heap_fctl->heap_fwork_cachep, heap_fwork);
>>> +}
>>> +
>>> +int dma_heap_submit_file_read(struct dma_heap_file_task *heap_ftask)
>>> +{
>>> +    struct dma_heap_file_work *heap_fwork = 
>>> init_file_work(heap_ftask);
>>> +    struct page *last = NULL;
>>> +    struct dma_heap_file *heap_file = heap_ftask->heap_file;
>>> +    size_t start = heap_ftask->roffset;
>>> +    struct file *file = heap_file->file;
>>> +    size_t fsz = heap_file->fsz;
>>> +
>>> +    if (unlikely(!heap_fwork))
>>> +        return -ENOMEM;
>>> +
>>> +    /**
>>> +     * If file size is not page aligned, direct io can't process 
>>> the tail.
>>> +     * So, if reach to tail, remain the last page use buffer read.
>>> +     */
>>> +    if (heap_file->direct && start + heap_ftask->rsize > fsz) {
>>> +        heap_fwork->need_size -= PAGE_SIZE;
>>> +        last = heap_ftask->parray[heap_ftask->pindex - 1];
>>> +    }
>>> +
>>> +    spin_lock(&heap_fctl->lock);
>>> +    list_add_tail(&heap_fwork->list, &heap_fctl->works);
>>> +    spin_unlock(&heap_fctl->lock);
>>> +    atomic_inc(&heap_fctl->nr_work);
>>> +
>>> +    wake_up(&heap_fctl->threadwq);
>>> +
>>> +    if (last) {
>>> +        char *buf, *pathp;
>>> +        ssize_t err;
>>> +        void *buffer;
>>> +
>>> +        buf = kmalloc(PATH_MAX, GFP_KERNEL);
>>> +        if (unlikely(!buf))
>>> +            return -ENOMEM;
>>> +
>>> +        start = PAGE_ALIGN_DOWN(fsz);
>>> +
>>> +        pathp = file_path(file, buf, PATH_MAX);
>>> +        if (IS_ERR(pathp)) {
>>> +            kfree(buf);
>>> +            return PTR_ERR(pathp);
>>> +        }
>>> +
>>> +        buffer = kmap_local_page(last); // use page's kaddr.
>>> +        err = kernel_read_file_from_path(pathp, start, &buffer,
>>> +                         fsz - start, &fsz,
>>> +                         READING_POLICY);
>>> +        kunmap_local(buffer);
>>> +        kfree(buf);
>>> +        if (err < 0) {
>>> +            pr_err("failed to use buffer kernel_read_file %s, 
>>> err=%ld, [%ld, %ld], f_sz=%ld\n",
>>> +                   pathp, err, start, fsz, fsz);
>>> +
>>> +            return err;
>>> +        }
>>> +    }
>>> +
>>> +    heap_ftask->roffset += heap_ftask->rsize;
>>> +    heap_ftask->rsize = 0;
>>> +    heap_ftask->pindex = 0;
>>> +    heap_ftask->rbatch = min_t(size_t,
>>> +                   PAGE_ALIGN(fsz) - heap_ftask->roffset,
>>> +                   heap_ftask->rbatch);
>>> +    return 0;
>>> +}
>>> +
>>> +bool dma_heap_wait_for_file_read(struct dma_heap_file_task 
>>> *heap_ftask)
>>> +{
>>> +    wait_event_freezable(heap_fctl->workwq,
>>> +                 atomic_read(&heap_ftask->ref) == 0);
>>> +    return heap_ftask->fail;
>>> +}
>>> +
>>> +bool dma_heap_destroy_file_read(struct dma_heap_file_task *heap_ftask)
>>> +{
>>> +    bool fail;
>>> +
>>> +    dma_heap_wait_for_file_read(heap_ftask);
>>> +    fail = heap_ftask->fail;
>>> +    kvfree(heap_ftask->parray);
>>> +    kfree(heap_ftask);
>>> +    return fail;
>>> +}
>>> +
>>> +struct dma_heap_file_task *
>>> +dma_heap_declare_file_read(struct dma_heap_file *heap_file)
>>> +{
>>> +    struct dma_heap_file_task *heap_ftask =
>>> +        kzalloc(sizeof(*heap_ftask), GFP_KERNEL);
>>> +    if (unlikely(!heap_ftask))
>>> +        return NULL;
>>> +
>>> +    /**
>>> +     * Batch is the maximum size which we prepare work will meet.
>>> +     * So, direct alloc this number's page array is OK.
>>> +     */
>>> +    heap_ftask->parray = kvmalloc_array(heap_file->max_batch >> 
>>> PAGE_SHIFT,
>>> +                        sizeof(struct page *), GFP_KERNEL);
>>> +    if (unlikely(!heap_ftask->parray))
>>> +        goto put;
>>> +
>>> +    heap_ftask->heap_file = heap_file;
>>> +    heap_ftask->rbatch = heap_file->max_batch;
>>> +    return heap_ftask;
>>> +put:
>>> +    kfree(heap_ftask);
>>> +    return NULL;
>>> +}
>>> +
>>> +static void __work_this_io(struct dma_heap_file_work *heap_fwork)
>>> +{
>>> +    struct dma_heap_file *heap_file = heap_fwork->heap_file;
>>> +    struct file *file = heap_file->file;
>>> +    ssize_t start = heap_fwork->start_size;
>>> +    ssize_t size = heap_fwork->need_size;
>>> +    void *buffer = heap_fwork->vaddr;
>>> +    const struct cred *old_cred;
>>> +    ssize_t err;
>>> +
>>> +    // use real task's cred to read this file.
>>> +    old_cred = override_creds(heap_file->cred);
>>> +    err = kernel_read_file(file, start, &buffer, size, 
>>> &heap_file->fsz,
>>> +                   READING_POLICY);
>>> +    if (err < 0) {
>>> +        pr_err("use kernel_read_file, err=%ld, [%ld, %ld], 
>>> f_sz=%ld\n",
>>> +               err, start, (start + size), heap_file->fsz);
>>> +        WRITE_ONCE(*heap_fwork->failp, true);
>>> +    }
>>> +    // recovery to my cred.
>>> +    revert_creds(old_cred);
>>> +}
>>> +
>>> +static int dma_heap_file_control_thread(void *data)
>>> +{
>>> +    struct dma_heap_file_control *heap_fctl =
>>> +        (struct dma_heap_file_control *)data;
>>> +    struct dma_heap_file_work *worker, *tmp;
>>> +    int nr_work;
>>> +
>>> +    LIST_HEAD(pages);
>>> +    LIST_HEAD(workers);
>>> +
>>> +    while (true) {
>>> +        wait_event_freezable(heap_fctl->threadwq,
>>> +                     atomic_read(&heap_fctl->nr_work) > 0);
>>> +recheck:
>>> +        spin_lock(&heap_fctl->lock);
>>> +        list_splice_init(&heap_fctl->works, &workers);
>>> +        spin_unlock(&heap_fctl->lock);
>>> +
>>> +        if (unlikely(kthread_should_stop())) {
>>> +            list_for_each_entry_safe(worker, tmp, &workers, list) {
>>> +                list_del(&worker->list);
>>> +                destroy_file_work(worker);
>>> +            }
>>> +            break;
>>> +        }
>>> +
>>> +        nr_work = 0;
>>> +        list_for_each_entry_safe(worker, tmp, &workers, list) {
>>> +            ++nr_work;
>>> +            list_del(&worker->list);
>>> +            __work_this_io(worker);
>>> +
>>> +            destroy_file_work(worker);
>>> +        }
>>> +        atomic_sub(nr_work, &heap_fctl->nr_work);
>>> +
>>> +        if (atomic_read(&heap_fctl->nr_work) > 0)
>>> +            goto recheck;
>>> +    }
>>> +    return 0;
>>> +}
>>> +
>>> +size_t dma_heap_file_size(struct dma_heap_file *heap_file)
>>> +{
>>> +    return heap_file->fsz;
>>> +}
>>> +
>>> +static int prepare_dma_heap_file(struct dma_heap_file *heap_file, 
>>> int file_fd,
>>> +                 size_t batch)
>>> +{
>>> +    struct file *file;
>>> +    size_t fsz;
>>> +    int ret;
>>> +
>>> +    file = fget(file_fd);
>>> +    if (!file)
>>> +        return -EINVAL;
>>> +
>>> +    fsz = i_size_read(file_inode(file));
>>> +    if (fsz < batch) {
>>> +        ret = -EINVAL;
>>> +        goto err;
>>> +    }
>>> +
>>> +    /**
>>> +     * Selinux block our read, but actually we are reading the 
>>> stand-in
>>> +     * for this file.
>>> +     * So save current's cred and when going to read, override 
>>> mine, and
>>> +     * end of read, revert.
>>> +     */
>>> +    heap_file->cred = prepare_kernel_cred(current);
>>> +    if (unlikely(!heap_file->cred)) {
>>> +        ret = -ENOMEM;
>>> +        goto err;
>>> +    }
>>> +
>>> +    heap_file->file = file;
>>> +    heap_file->max_batch = batch;
>>> +    heap_file->fsz = fsz;
>>> +
>>> +    heap_file->direct = file->f_flags & O_DIRECT;
>>> +
>>> +#define DMA_HEAP_SUGGEST_DIRECT_IO_SIZE (1UL << 30)
>>> +    if (!heap_file->direct && fsz >= DMA_HEAP_SUGGEST_DIRECT_IO_SIZE)
>>> +        pr_warn("alloc read file better to use O_DIRECT to read 
>>> larget file\n");
>>> +
>>> +    return 0;
>>> +
>>> +err:
>>> +    fput(file);
>>> +    return ret;
>>> +}
>>> +
>>> +static void destroy_dma_heap_file(struct dma_heap_file *heap_file)
>>> +{
>>> +    fput(heap_file->file);
>>> +    put_cred(heap_file->cred);
>>> +}
>>> +
>>> +static int dma_heap_buffer_alloc_read_file(struct dma_heap *heap, 
>>> int file_fd,
>>> +                       size_t batch, unsigned int fd_flags,
>>> +                       unsigned int heap_flags)
>>> +{
>>> +    struct dma_buf *dmabuf;
>>> +    int fd;
>>> +    struct dma_heap_file heap_file;
>>> +
>>> +    fd = prepare_dma_heap_file(&heap_file, file_fd, batch);
>>> +    if (fd)
>>> +        goto error_file;
>>> +
>>> +    dmabuf = heap->ops->allocate_read_file(heap, &heap_file, fd_flags,
>>> +                           heap_flags);
>>> +    if (IS_ERR(dmabuf)) {
>>> +        fd = PTR_ERR(dmabuf);
>>> +        goto error;
>>> +    }
>>> +
>>> +    fd = dma_buf_fd(dmabuf, fd_flags);
>>> +    if (fd < 0) {
>>> +        dma_buf_put(dmabuf);
>>> +        /* just return, as put will call release and that will free */
>>> +    }
>>> +
>>> +error:
>>> +    destroy_dma_heap_file(&heap_file);
>>> +error_file:
>>> +    return fd;
>>> +}
>>> +
>>>   static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
>>>                    u32 fd_flags,
>>>                    u64 heap_flags)
>>> @@ -93,6 +545,38 @@ static int dma_heap_open(struct inode *inode, 
>>> struct file *file)
>>>       return 0;
>>>   }
>>>   +static long dma_heap_ioctl_allocate_read_file(struct file *file, 
>>> void *data)
>>> +{
>>> +    struct dma_heap_allocation_file_data *heap_allocation_file = data;
>>> +    struct dma_heap *heap = file->private_data;
>>> +    int fd;
>>> +
>>> +    if (heap_allocation_file->fd || !heap_allocation_file->file_fd)
>>> +        return -EINVAL;
>>> +
>>> +    if (heap_allocation_file->fd_flags & ~DMA_HEAP_VALID_FD_FLAGS)
>>> +        return -EINVAL;
>>> +
>>> +    if (heap_allocation_file->heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
>>> +        return -EINVAL;
>>> +
>>> +    if (!heap->ops->allocate_read_file)
>>> +        return -EINVAL;
>>> +
>>> +    fd = dma_heap_buffer_alloc_read_file(
>>> +        heap, heap_allocation_file->file_fd,
>>> +        heap_allocation_file->batch ?
>>> +            PAGE_ALIGN(heap_allocation_file->batch) :
>>> +            DEFAULT_ADI_BATCH,
>>> +        heap_allocation_file->fd_flags,
>>> +        heap_allocation_file->heap_flags);
>>> +    if (fd < 0)
>>> +        return fd;
>>> +
>>> +    heap_allocation_file->fd = fd;
>>> +    return 0;
>>> +}
>>> +
>>>   static long dma_heap_ioctl_allocate(struct file *file, void *data)
>>>   {
>>>       struct dma_heap_allocation_data *heap_allocation = data;
>>> @@ -121,6 +605,7 @@ static long dma_heap_ioctl_allocate(struct file 
>>> *file, void *data)
>>>     static unsigned int dma_heap_ioctl_cmds[] = {
>>>       DMA_HEAP_IOCTL_ALLOC,
>>> +    DMA_HEAP_IOCTL_ALLOC_AND_READ,
>>>   };
>>>     static long dma_heap_ioctl(struct file *file, unsigned int ucmd,
>>> @@ -170,6 +655,9 @@ static long dma_heap_ioctl(struct file *file, 
>>> unsigned int ucmd,
>>>       case DMA_HEAP_IOCTL_ALLOC:
>>>           ret = dma_heap_ioctl_allocate(file, kdata);
>>>           break;
>>> +    case DMA_HEAP_IOCTL_ALLOC_AND_READ:
>>> +        ret = dma_heap_ioctl_allocate_read_file(file, kdata);
>>> +        break;
>>>       default:
>>>           ret = -ENOTTY;
>>>           goto err;
>>> @@ -316,11 +804,44 @@ static int dma_heap_init(void)
>>>         dma_heap_class = class_create(DEVNAME);
>>>       if (IS_ERR(dma_heap_class)) {
>>> -        unregister_chrdev_region(dma_heap_devt, NUM_HEAP_MINORS);
>>> -        return PTR_ERR(dma_heap_class);
>>> +        ret = PTR_ERR(dma_heap_class);
>>> +        goto fail_class;
>>>       }
>>>       dma_heap_class->devnode = dma_heap_devnode;
>>>   +    heap_fctl = kzalloc(sizeof(*heap_fctl), GFP_KERNEL);
>>> +    if (unlikely(!heap_fctl)) {
>>> +        ret =  -ENOMEM;
>>> +        goto fail_alloc;
>>> +    }
>>> +
>>> +    INIT_LIST_HEAD(&heap_fctl->works);
>>> +    init_waitqueue_head(&heap_fctl->threadwq);
>>> +    init_waitqueue_head(&heap_fctl->workwq);
>>> +
>>> +    heap_fctl->work_thread = kthread_run(dma_heap_file_control_thread,
>>> +                         heap_fctl, "heap_fwork_t");
>>> +    if (IS_ERR(heap_fctl->work_thread)) {
>>> +        ret = -ENOMEM;
>>> +        goto fail_thread;
>>> +    }
>>> +
>>> +    heap_fctl->heap_fwork_cachep = KMEM_CACHE(dma_heap_file_work, 0);
>>> +    if (unlikely(!heap_fctl->heap_fwork_cachep)) {
>>> +        ret = -ENOMEM;
>>> +        goto fail_cache;
>>> +    }
>>> +
>>>       return 0;
>>> +
>>> +fail_cache:
>>> +    kthread_stop(heap_fctl->work_thread);
>>> +fail_thread:
>>> +    kfree(heap_fctl);
>>> +fail_alloc:
>>> +    class_destroy(dma_heap_class);
>>> +fail_class:
>>> +    unregister_chrdev_region(dma_heap_devt, NUM_HEAP_MINORS);
>>> +    return ret;
>>>   }
>>>   subsys_initcall(dma_heap_init);
>>> diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
>>> index 064bad725061..9c25383f816c 100644
>>> --- a/include/linux/dma-heap.h
>>> +++ b/include/linux/dma-heap.h
>>> @@ -12,12 +12,17 @@
>>>   #include <linux/cdev.h>
>>>   #include <linux/types.h>
>>>   +#define DEFAULT_ADI_BATCH (128 << 20)
>>> +
>>>   struct dma_heap;
>>> +struct dma_heap_file_task;
>>> +struct dma_heap_file;
>>>     /**
>>>    * struct dma_heap_ops - ops to operate on a given heap
>>>    * @allocate:        allocate dmabuf and return struct dma_buf ptr
>>> - *
>>> + * @allocate_read_file: allocate dmabuf and read file, then return 
>>> struct
>>> + * dma_buf ptr.
>>>    * allocate returns dmabuf on success, ERR_PTR(-errno) on error.
>>>    */
>>>   struct dma_heap_ops {
>>> @@ -25,6 +30,11 @@ struct dma_heap_ops {
>>>                       unsigned long len,
>>>                       u32 fd_flags,
>>>                       u64 heap_flags);
>>> +
>>> +    struct dma_buf *(*allocate_read_file)(struct dma_heap *heap,
>>> +                          struct dma_heap_file *heap_file,
>>> +                          u32 fd_flags,
>>> +                          u64 heap_flags);
>>>   };
>>>     /**
>>> @@ -65,4 +75,49 @@ const char *dma_heap_get_name(struct dma_heap 
>>> *heap);
>>>    */
>>>   struct dma_heap *dma_heap_add(const struct dma_heap_export_info 
>>> *exp_info);
>>>   +/**
>>> + * dma_heap_destroy_file_read - waits for a file read to complete 
>>> then destroy it
>>> + * Returns: true if the file read failed, false otherwise
>>> + */
>>> +bool dma_heap_destroy_file_read(struct dma_heap_file_task 
>>> *heap_ftask);
>>> +
>>> +/**
>>> + * dma_heap_wait_for_file_read - waits for a file read to complete
>>> + * Returns: true if the file read failed, false otherwise
>>> + */
>>> +bool dma_heap_wait_for_file_read(struct dma_heap_file_task 
>>> *heap_ftask);
>>> +
>>> +/**
>>> + * dma_heap_alloc_file_read - Declare a task to read file when 
>>> allocate pages.
>>> + * @heap_file:        target file to read
>>> + *
>>> + * Return NULL if failed, otherwise return a struct pointer.
>>> + */
>>> +struct dma_heap_file_task *
>>> +dma_heap_declare_file_read(struct dma_heap_file *heap_file);
>>> +
>>> +/**
>>> + * dma_heap_prepare_file_read - cache each allocated page until we 
>>> meet this batch.
>>> + * @heap_ftask:        prepared and need to commit's work.
>>> + * @page:        current allocated page. don't care which order.
>>> + *
>>> + * Returns true if reach to batch, false so go on prepare.
>>> + */
>>> +bool dma_heap_prepare_file_read(struct dma_heap_file_task *heap_ftask,
>>> +                struct page *page);
>>> +
>>> +/**
>>> + * dma_heap_commit_file_read -  prepare collect enough memory, 
>>> going to trigger IO
>>> + * @heap_ftask:            info that current IO needs
>>> + *
>>> + * This commit will also check if reach to tail read.
>>> + * For direct I/O submissions, it is necessary to pay attention to 
>>> file reads
>>> + * that are not page-aligned. For the unaligned portion of the 
>>> read, buffer IO
>>> + * needs to be triggered.
>>> + * Returns:
>>> + *   0 if all right, -errno if something wrong
>>> + */
>>> +int dma_heap_submit_file_read(struct dma_heap_file_task *heap_ftask);
>>> +size_t dma_heap_file_size(struct dma_heap_file *heap_file);
>>> +
>>>   #endif /* _DMA_HEAPS_H */
>>> diff --git a/include/uapi/linux/dma-heap.h 
>>> b/include/uapi/linux/dma-heap.h
>>> index a4cf716a49fa..8c20e8b74eed 100644
>>> --- a/include/uapi/linux/dma-heap.h
>>> +++ b/include/uapi/linux/dma-heap.h
>>> @@ -39,6 +39,27 @@ struct dma_heap_allocation_data {
>>>       __u64 heap_flags;
>>>   };
>>>   +/**
>>> + * struct dma_heap_allocation_file_data - metadata passed from 
>>> userspace for
>>> + *                                      allocations and read file
>>> + * @fd:            will be populated with a fd which provides the
>>> + *            handle to the allocated dma-buf
>>> + * @file_fd:        file descriptor to read from(suggested to use 
>>> O_DIRECT open file)
>>> + * @batch:        how many memory alloced then file read(bytes), 
>>> default 128MB
>>> + *            will auto aligned to PAGE_SIZE
>>> + * @fd_flags:        file descriptor flags used when allocating
>>> + * @heap_flags:        flags passed to heap
>>> + *
>>> + * Provided by userspace as an argument to the ioctl
>>> + */
>>> +struct dma_heap_allocation_file_data {
>>> +    __u32 fd;
>>> +    __u32 file_fd;
>>> +    __u32 batch;
>>> +    __u32 fd_flags;
>>> +    __u64 heap_flags;
>>> +};
>>> +
>>>   #define DMA_HEAP_IOC_MAGIC        'H'
>>>     /**
>>> @@ -50,4 +71,15 @@ struct dma_heap_allocation_data {
>>>   #define DMA_HEAP_IOCTL_ALLOC    _IOWR(DMA_HEAP_IOC_MAGIC, 0x0,\
>>>                         struct dma_heap_allocation_data)
>>>   +/**
>>> + * DOC: DMA_HEAP_IOCTL_ALLOC_AND_READ - allocate memory from pool 
>>> and both
>>> + *                    read file when allocate memory.
>>> + *
>>> + * Takes a dma_heap_allocation_file_data struct and returns it with 
>>> the fd field
>>> + * populated with the dmabuf handle of the allocation. When return, 
>>> the dma-buf
>>> + * content is read from file.
>>> + */
>>> +#define DMA_HEAP_IOCTL_ALLOC_AND_READ \
>>> +    _IOWR(DMA_HEAP_IOC_MAGIC, 0x1, struct 
>>> dma_heap_allocation_file_data)
>>> +
>>>   #endif /* _UAPI_LINUX_DMABUF_POOL_H */
>>

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