/*
 * Copyright (c) 2005 Topspin Communications.  All rights reserved.
 * Copyright (c) 2005 Cisco Systems.  All rights reserved.
 * Copyright (c) 2005 Mellanox Technologies. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/mm.h>
#include <linux/dma-mapping.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/export.h>
#include <linux/hugetlb.h>
#include <linux/slab.h>
#include <rdma/ib_umem_odp.h>

#include "uverbs.h"


static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int dirty)
{
        struct scatterlist *sg;
        struct page *page;
        int i;

        if (umem->nmap > 0)
                ib_dma_unmap_sg(dev, umem->sg_head.sgl,
                                umem->npages,
                                DMA_BIDIRECTIONAL);

        for_each_sg(umem->sg_head.sgl, sg, umem->npages, i) {

                page = sg_page(sg);
                if (umem->writable && dirty)
                        set_page_dirty_lock(page);
                put_page(page);
        }

        sg_free_table(&umem->sg_head);
        return;

}

/**
 * ib_umem_get - Pin and DMA map userspace memory.
 *
 * If access flags indicate ODP memory, avoid pinning. Instead, stores
 * the mm for future page fault handling in conjunction with MMU notifiers.
 *
 * @context: userspace context to pin memory for
 * @addr: userspace virtual address to start at
 * @size: length of region to pin
 * @access: IB_ACCESS_xxx flags for memory being pinned
 * @dmasync: flush in-flight DMA when the memory region is written
 */
struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
                            size_t size, int access, int dmasync)
{
        struct ib_umem *umem;
        struct page **page_list;
        struct vm_area_struct **vma_list;
        unsigned long locked;
        unsigned long lock_limit;
        unsigned long cur_base;
        unsigned long npages;
        int ret;
        int i;
        unsigned long dma_attrs = 0;
        struct scatterlist *sg, *sg_list_start;
        int need_release = 0;
        unsigned int gup_flags = FOLL_WRITE;

        if (dmasync)
                dma_attrs |= DMA_ATTR_WRITE_BARRIER;

        /*
         * If the combination of the addr and size requested for this memory
         * region causes an integer overflow, return error.
         */
        if (((addr + size) < addr) ||
            PAGE_ALIGN(addr + size) < (addr + size))
                return ERR_PTR(-EINVAL);

        if (!can_do_mlock())
                return ERR_PTR(-EPERM);

        umem = kzalloc(sizeof *umem, GFP_KERNEL);
        if (!umem)
                return ERR_PTR(-ENOMEM);

        umem->context   = context;
        umem->length    = size;
        umem->address   = addr;
        umem->page_size = PAGE_SIZE;
        umem->pid       = get_task_pid(current, PIDTYPE_PID);
        /*
         * We ask for writable memory if any of the following
         * access flags are set.  "Local write" and "remote write"
         * obviously require write access.  "Remote atomic" can do
         * things like fetch and add, which will modify memory, and
         * "MW bind" can change permissions by binding a window.
         */
        umem->writable  = !!(access &
                (IB_ACCESS_LOCAL_WRITE   | IB_ACCESS_REMOTE_WRITE |
                 IB_ACCESS_REMOTE_ATOMIC | IB_ACCESS_MW_BIND));

        if (access & IB_ACCESS_ON_DEMAND) {
                put_pid(umem->pid);
                ret = ib_umem_odp_get(context, umem);
                if (ret) {
                        kfree(umem);
                        return ERR_PTR(ret);
                }
                return umem;
        }

        umem->odp_data = NULL;

        /* We assume the memory is from hugetlb until proved otherwise */
        umem->hugetlb   = 1;

        page_list = (struct page **) __get_free_page(GFP_KERNEL);
        if (!page_list) {
                put_pid(umem->pid);
                kfree(umem);
                return ERR_PTR(-ENOMEM);
        }

        /*
         * if we can't alloc the vma_list, it's not so bad;
         * just assume the memory is not hugetlb memory
         */
        vma_list = (struct vm_area_struct **) __get_free_page(GFP_KERNEL);
        if (!vma_list)
                umem->hugetlb = 0;

        npages = ib_umem_num_pages(umem);

        down_write(&current->mm->mmap_sem);

        locked     = npages + current->mm->pinned_vm;
        lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
                ret = -ENOMEM;
                goto out;
        }

        cur_base = addr & PAGE_MASK;

        if (npages == 0 || npages > UINT_MAX) {
                ret = -EINVAL;
                goto out;
        }

        ret = sg_alloc_table(&umem->sg_head, npages, GFP_KERNEL);
        if (ret)
                goto out;

        if (!umem->writable)
                gup_flags |= FOLL_FORCE;

        need_release = 1;
        sg_list_start = umem->sg_head.sgl;

        while (npages) {
                ret = get_user_pages(cur_base,
                                     min_t(unsigned long, npages,
                                           PAGE_SIZE / sizeof (struct page *)),
                                     gup_flags, page_list, vma_list);

                if (ret < 0)
                        goto out;

                umem->npages += ret;
                cur_base += ret * PAGE_SIZE;
                npages   -= ret;

                for_each_sg(sg_list_start, sg, ret, i) {
                        if (vma_list && !is_vm_hugetlb_page(vma_list[i]))
                                umem->hugetlb = 0;

                        sg_set_page(sg, page_list[i], PAGE_SIZE, 0);
                }

                /* preparing for next loop */
                sg_list_start = sg;
        }

        umem->nmap = ib_dma_map_sg_attrs(context->device,
                                  umem->sg_head.sgl,
                                  umem->npages,
                                  DMA_BIDIRECTIONAL,
                                  dma_attrs);

        if (umem->nmap <= 0) {
                ret = -ENOMEM;
                goto out;
        }

        ret = 0;

out:
        if (ret < 0) {
                if (need_release)
                        __ib_umem_release(context->device, umem, 0);
                put_pid(umem->pid);
                kfree(umem);
        } else
                current->mm->pinned_vm = locked;

        up_write(&current->mm->mmap_sem);
        if (vma_list)
                free_page((unsigned long) vma_list);
        free_page((unsigned long) page_list);

        return ret < 0 ? ERR_PTR(ret) : umem;
}
EXPORT_SYMBOL(ib_umem_get);

static void ib_umem_account(struct work_struct *work)
{
        struct ib_umem *umem = container_of(work, struct ib_umem, work);

        down_write(&umem->mm->mmap_sem);
        umem->mm->pinned_vm -= umem->diff;
        up_write(&umem->mm->mmap_sem);
        mmput(umem->mm);
        kfree(umem);
}

/**
 * ib_umem_release - release memory pinned with ib_umem_get
 * @umem: umem struct to release
 */
void ib_umem_release(struct ib_umem *umem)
{
        struct ib_ucontext *context = umem->context;
        struct mm_struct *mm;
        struct task_struct *task;
        unsigned long diff;

        if (umem->odp_data) {
                ib_umem_odp_release(umem);
                return;
        }

        __ib_umem_release(umem->context->device, umem, 1);

        task = get_pid_task(umem->pid, PIDTYPE_PID);
        put_pid(umem->pid);
        if (!task)
                goto out;
        mm = get_task_mm(task);
        put_task_struct(task);
        if (!mm)
                goto out;

        diff = ib_umem_num_pages(umem);

        /*
         * We may be called with the mm's mmap_sem already held.  This
         * can happen when a userspace munmap() is the call that drops
         * the last reference to our file and calls our release
         * method.  If there are memory regions to destroy, we'll end
         * up here and not be able to take the mmap_sem.  In that case
         * we defer the vm_locked accounting to the system workqueue.
         */
        if (context->closing) {
                if (!down_write_trylock(&mm->mmap_sem)) {
                        INIT_WORK(&umem->work, ib_umem_account);
                        umem->mm   = mm;
                        umem->diff = diff;

                        queue_work(ib_wq, &umem->work);
                        return;
                }
        } else
                down_write(&mm->mmap_sem);

        mm->pinned_vm -= diff;
        up_write(&mm->mmap_sem);
        mmput(mm);
out:
        kfree(umem);
}
EXPORT_SYMBOL(ib_umem_release);

int ib_umem_page_count(struct ib_umem *umem)
{
        int shift;
        int i;
        int n;
        struct scatterlist *sg;

        if (umem->odp_data)
                return ib_umem_num_pages(umem);

        shift = ilog2(umem->page_size);

        n = 0;
        for_each_sg(umem->sg_head.sgl, sg, umem->nmap, i)
                n += sg_dma_len(sg) >> shift;

        return n;
}
EXPORT_SYMBOL(ib_umem_page_count);

/*
 * Copy from the given ib_umem's pages to the given buffer.
 *
 * umem - the umem to copy from
 * offset - offset to start copying from
 * dst - destination buffer
 * length - buffer length
 *
 * Returns 0 on success, or an error code.
 */
int ib_umem_copy_from(void *dst, struct ib_umem *umem, size_t offset,
                      size_t length)
{
        size_t end = offset + length;
        int ret;

        if (offset > umem->length || length > umem->length - offset) {
                pr_err("ib_umem_copy_from not in range. offset: %zd umem length: %zd end: %zd\n",
                       offset, umem->length, end);
                return -EINVAL;
        }

        ret = sg_pcopy_to_buffer(umem->sg_head.sgl, umem->nmap, dst, length,
                                 offset + ib_umem_offset(umem));

        if (ret < 0)
                return ret;
        else if (ret != length)
                return -EINVAL;
        else
                return 0;
}
EXPORT_SYMBOL(ib_umem_copy_from);