/*
 * Copyright (c) 2014 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/types.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/task.h>
#include <linux/pid.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/hugetlb.h>
#include <linux/interval_tree.h>
#include <linux/hmm.h>
#include <linux/hmm-dma.h>
#include <linux/pagemap.h>

#include <rdma/ib_umem_odp.h>

#include "uverbs.h"

static void ib_init_umem_implicit_odp(struct ib_umem_odp *umem_odp)
{
        umem_odp->is_implicit_odp = 1;
        umem_odp->umem.is_odp = 1;
        mutex_init(&umem_odp->umem_mutex);
}

static int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
                            const struct mmu_interval_notifier_ops *ops)
{
        struct ib_device *dev = umem_odp->umem.ibdev;
        size_t page_size = 1UL << umem_odp->page_shift;
        struct hmm_dma_map *map;
        unsigned long start;
        unsigned long end;
        size_t nr_entries;
        int ret = 0;

        umem_odp->umem.is_odp = 1;
        mutex_init(&umem_odp->umem_mutex);

        start = ALIGN_DOWN(umem_odp->umem.address, page_size);
        if (check_add_overflow(umem_odp->umem.address,
                               (unsigned long)umem_odp->umem.length, &end))
                return -EOVERFLOW;
        end = ALIGN(end, page_size);
        if (unlikely(end < page_size))
                return -EOVERFLOW;
        /*
         * The mmu notifier can be called within reclaim contexts and takes the
         * umem_mutex. This is rare to trigger in testing, teach lockdep about
         * it.
         */
        if (IS_ENABLED(CONFIG_LOCKDEP)) {
                fs_reclaim_acquire(GFP_KERNEL);
                mutex_lock(&umem_odp->umem_mutex);
                mutex_unlock(&umem_odp->umem_mutex);
                fs_reclaim_release(GFP_KERNEL);
        }

        nr_entries = (end - start) >> PAGE_SHIFT;
        if (!(nr_entries * PAGE_SIZE / page_size))
                return -EINVAL;

        map = &umem_odp->map;
        if (ib_uses_virt_dma(dev)) {
                map->pfn_list = kvcalloc(nr_entries, sizeof(*map->pfn_list),
                                         GFP_KERNEL | __GFP_NOWARN);
                if (!map->pfn_list)
                        ret = -ENOMEM;
        } else
                ret = hmm_dma_map_alloc(dev->dma_device, map,
                                        (end - start) >> PAGE_SHIFT,
                                        1 << umem_odp->page_shift);
        if (ret)
                return ret;

        ret = mmu_interval_notifier_insert(&umem_odp->notifier,
                                           umem_odp->umem.owning_mm, start,
                                           end - start, ops);
        if (ret)
                goto out_free_map;

        return 0;

out_free_map:
        if (ib_uses_virt_dma(dev))
                kvfree(map->pfn_list);
        else
                hmm_dma_map_free(dev->dma_device, map);
        return ret;
}

/**
 * ib_umem_odp_alloc_implicit - Allocate a parent implicit ODP umem
 *
 * Implicit ODP umems do not have a VA range and do not have any page lists.
 * They exist only to hold the per_mm reference to help the driver create
 * children umems.
 *
 * @device: IB device to create UMEM
 * @access: ib_reg_mr access flags
 */
struct ib_umem_odp *ib_umem_odp_alloc_implicit(struct ib_device *device,
                                               int access)
{
        struct ib_umem *umem;
        struct ib_umem_odp *umem_odp;

        if (access & IB_ACCESS_HUGETLB)
                return ERR_PTR(-EINVAL);

        umem_odp = kzalloc_obj(*umem_odp);
        if (!umem_odp)
                return ERR_PTR(-ENOMEM);
        umem = &umem_odp->umem;
        umem->ibdev = device;
        umem->writable = ib_access_writable(access);
        umem->owning_mm = current->mm;
        umem_odp->page_shift = PAGE_SHIFT;

        umem_odp->tgid = get_task_pid(current, PIDTYPE_TGID);
        ib_init_umem_implicit_odp(umem_odp);
        return umem_odp;
}
EXPORT_SYMBOL(ib_umem_odp_alloc_implicit);

/**
 * ib_umem_odp_alloc_child - Allocate a child ODP umem under an implicit
 *                           parent ODP umem
 *
 * @root: The parent umem enclosing the child. This must be allocated using
 *        ib_alloc_implicit_odp_umem()
 * @addr: The starting userspace VA
 * @size: The length of the userspace VA
 * @ops: MMU interval ops, currently only @invalidate
 */
struct ib_umem_odp *
ib_umem_odp_alloc_child(struct ib_umem_odp *root, unsigned long addr,
                        size_t size,
                        const struct mmu_interval_notifier_ops *ops)
{
        /*
         * Caller must ensure that root cannot be freed during the call to
         * ib_alloc_odp_umem.
         */
        struct ib_umem_odp *odp_data;
        struct ib_umem *umem;
        int ret;

        if (WARN_ON(!root->is_implicit_odp))
                return ERR_PTR(-EINVAL);

        odp_data = kzalloc_obj(*odp_data);
        if (!odp_data)
                return ERR_PTR(-ENOMEM);
        umem = &odp_data->umem;
        umem->ibdev = root->umem.ibdev;
        umem->length     = size;
        umem->address    = addr;
        umem->writable   = root->umem.writable;
        umem->owning_mm  = root->umem.owning_mm;
        odp_data->page_shift = PAGE_SHIFT;
        odp_data->notifier.ops = ops;

        /*
         * A mmget must be held when registering a notifier, the owming_mm only
         * has a mm_grab at this point.
         */
        if (!mmget_not_zero(umem->owning_mm)) {
                ret = -EFAULT;
                goto out_free;
        }

        odp_data->tgid = get_pid(root->tgid);
        ret = ib_init_umem_odp(odp_data, ops);
        if (ret)
                goto out_tgid;
        mmput(umem->owning_mm);
        return odp_data;

out_tgid:
        put_pid(odp_data->tgid);
        mmput(umem->owning_mm);
out_free:
        kfree(odp_data);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL(ib_umem_odp_alloc_child);

/**
 * ib_umem_odp_get - Create a umem_odp for a userspace va
 *
 * @device: IB device struct to get UMEM
 * @addr: userspace virtual address to start at
 * @size: length of region to pin
 * @access: IB_ACCESS_xxx flags for memory being pinned
 * @ops: MMU interval ops, currently only @invalidate
 *
 * The driver should use when the access flags indicate ODP memory. It avoids
 * pinning, instead, stores the mm for future page fault handling in
 * conjunction with MMU notifiers.
 */
struct ib_umem_odp *ib_umem_odp_get(struct ib_device *device,
                                    unsigned long addr, size_t size, int access,
                                    const struct mmu_interval_notifier_ops *ops)
{
        struct ib_umem_odp *umem_odp;
        int ret;

        if (WARN_ON_ONCE(!(access & IB_ACCESS_ON_DEMAND)))
                return ERR_PTR(-EINVAL);

        umem_odp = kzalloc_obj(struct ib_umem_odp);
        if (!umem_odp)
                return ERR_PTR(-ENOMEM);

        umem_odp->umem.ibdev = device;
        umem_odp->umem.length = size;
        umem_odp->umem.address = addr;
        umem_odp->umem.writable = ib_access_writable(access);
        umem_odp->umem.owning_mm = current->mm;
        umem_odp->notifier.ops = ops;

        umem_odp->page_shift = PAGE_SHIFT;
#ifdef CONFIG_HUGETLB_PAGE
        if (access & IB_ACCESS_HUGETLB)
                umem_odp->page_shift = HPAGE_SHIFT;
#endif

        umem_odp->tgid = get_task_pid(current, PIDTYPE_TGID);
        ret = ib_init_umem_odp(umem_odp, ops);
        if (ret)
                goto err_put_pid;
        return umem_odp;

err_put_pid:
        put_pid(umem_odp->tgid);
        kfree(umem_odp);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL(ib_umem_odp_get);

static void ib_umem_odp_free(struct ib_umem_odp *umem_odp)
{
        struct ib_device *dev = umem_odp->umem.ibdev;

        /*
         * Ensure that no more pages are mapped in the umem.
         *
         * It is the driver's responsibility to ensure, before calling us,
         * that the hardware will not attempt to access the MR any more.
         */
        mutex_lock(&umem_odp->umem_mutex);
        ib_umem_odp_unmap_dma_pages(umem_odp, ib_umem_start(umem_odp),
                                    ib_umem_end(umem_odp));
        mutex_unlock(&umem_odp->umem_mutex);
        mmu_interval_notifier_remove(&umem_odp->notifier);
        if (ib_uses_virt_dma(dev))
                kvfree(umem_odp->map.pfn_list);
        else
                hmm_dma_map_free(dev->dma_device, &umem_odp->map);
}

void ib_umem_odp_release(struct ib_umem_odp *umem_odp)
{
        if (!umem_odp->is_implicit_odp)
                ib_umem_odp_free(umem_odp);

        put_pid(umem_odp->tgid);
        kfree(umem_odp);
}
EXPORT_SYMBOL(ib_umem_odp_release);

/**
 * ib_umem_odp_map_dma_and_lock - DMA map userspace memory in an ODP MR and lock it.
 *
 * Maps the range passed in the argument to DMA addresses.
 * Upon success the ODP MR will be locked to let caller complete its device
 * page table update.
 *
 * Returns the number of pages mapped in success, negative error code
 * for failure.
 * @umem_odp: the umem to map and pin
 * @user_virt: the address from which we need to map.
 * @bcnt: the minimal number of bytes to pin and map. The mapping might be
 *        bigger due to alignment, and may also be smaller in case of an error
 *        pinning or mapping a page. The actual pages mapped is returned in
 *        the return value.
 * @access_mask: bit mask of the requested access permissions for the given
 *               range.
 * @fault: is faulting required for the given range
 */
int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,
                                 u64 bcnt, u64 access_mask, bool fault)
                        __acquires(&umem_odp->umem_mutex)
{
        struct task_struct *owning_process  = NULL;
        struct mm_struct *owning_mm = umem_odp->umem.owning_mm;
        int pfn_index, dma_index, ret = 0, start_idx;
        unsigned int page_shift, hmm_order, pfn_start_idx;
        unsigned long num_pfns, current_seq;
        struct hmm_range range = {};
        unsigned long timeout;

        if (user_virt < ib_umem_start(umem_odp) ||
            user_virt + bcnt > ib_umem_end(umem_odp))
                return -EFAULT;

        page_shift = umem_odp->page_shift;

        /*
         * owning_process is allowed to be NULL, this means somehow the mm is
         * existing beyond the lifetime of the originating process.. Presumably
         * mmget_not_zero will fail in this case.
         */
        owning_process = get_pid_task(umem_odp->tgid, PIDTYPE_PID);
        if (!owning_process || !mmget_not_zero(owning_mm)) {
                ret = -EINVAL;
                goto out_put_task;
        }

        range.notifier = &umem_odp->notifier;
        range.start = ALIGN_DOWN(user_virt, 1UL << page_shift);
        range.end = ALIGN(user_virt + bcnt, 1UL << page_shift);
        pfn_start_idx = (range.start - ib_umem_start(umem_odp)) >> PAGE_SHIFT;
        num_pfns = (range.end - range.start) >> PAGE_SHIFT;
        if (fault) {
                range.default_flags = HMM_PFN_REQ_FAULT;

                if (access_mask & HMM_PFN_WRITE)
                        range.default_flags |= HMM_PFN_REQ_WRITE;
        }

        range.hmm_pfns = &(umem_odp->map.pfn_list[pfn_start_idx]);
        timeout = jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);

retry:
        current_seq = range.notifier_seq =
                mmu_interval_read_begin(&umem_odp->notifier);

        mmap_read_lock(owning_mm);
        ret = hmm_range_fault(&range);
        mmap_read_unlock(owning_mm);
        if (unlikely(ret)) {
                if (ret == -EBUSY && !time_after(jiffies, timeout))
                        goto retry;
                goto out_put_mm;
        }

        start_idx = (range.start - ib_umem_start(umem_odp)) >> page_shift;
        dma_index = start_idx;

        mutex_lock(&umem_odp->umem_mutex);
        if (mmu_interval_read_retry(&umem_odp->notifier, current_seq)) {
                mutex_unlock(&umem_odp->umem_mutex);
                goto retry;
        }

        for (pfn_index = 0; pfn_index < num_pfns;
                pfn_index += 1 << (page_shift - PAGE_SHIFT), dma_index++) {

                /*
                 * Since we asked for hmm_range_fault() to populate
                 * pages it shouldn't return an error entry on success.
                 */
                WARN_ON(fault && range.hmm_pfns[pfn_index] & HMM_PFN_ERROR);
                WARN_ON(fault && !(range.hmm_pfns[pfn_index] & HMM_PFN_VALID));
                if (!(range.hmm_pfns[pfn_index] & HMM_PFN_VALID))
                        continue;

                if (range.hmm_pfns[pfn_index] & HMM_PFN_DMA_MAPPED)
                        continue;

                hmm_order = hmm_pfn_to_map_order(range.hmm_pfns[pfn_index]);
                /* If a hugepage was detected and ODP wasn't set for, the umem
                 * page_shift will be used, the opposite case is an error.
                 */
                if (hmm_order + PAGE_SHIFT < page_shift) {
                        ret = -EINVAL;
                        ibdev_dbg(umem_odp->umem.ibdev,
                                  "%s: un-expected hmm_order %u, page_shift %u\n",
                                  __func__, hmm_order, page_shift);
                        break;
                }
        }
        /* upon success lock should stay on hold for the callee */
        if (!ret)
                ret = dma_index - start_idx;
        else
                mutex_unlock(&umem_odp->umem_mutex);

out_put_mm:
        mmput_async(owning_mm);
out_put_task:
        if (owning_process)
                put_task_struct(owning_process);
        return ret;
}
EXPORT_SYMBOL(ib_umem_odp_map_dma_and_lock);

void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
                                 u64 bound)
{
        struct ib_device *dev = umem_odp->umem.ibdev;
        u64 addr;

        lockdep_assert_held(&umem_odp->umem_mutex);

        virt = max_t(u64, virt, ib_umem_start(umem_odp));
        bound = min_t(u64, bound, ib_umem_end(umem_odp));
        for (addr = virt; addr < bound; addr += BIT(umem_odp->page_shift)) {
                u64 offset = addr - ib_umem_start(umem_odp);
                size_t idx = offset >> umem_odp->page_shift;
                unsigned long pfn = umem_odp->map.pfn_list[idx];

                if (!hmm_dma_unmap_pfn(dev->dma_device, &umem_odp->map, idx))
                        goto clear;

                if (pfn & HMM_PFN_WRITE) {
                        struct page *page = hmm_pfn_to_page(pfn);
                        struct page *head_page = compound_head(page);
                        /*
                         * set_page_dirty prefers being called with
                         * the page lock. However, MMU notifiers are
                         * called sometimes with and sometimes without
                         * the lock. We rely on the umem_mutex instead
                         * to prevent other mmu notifiers from
                         * continuing and allowing the page mapping to
                         * be removed.
                         */
                        set_page_dirty(head_page);
                }
                umem_odp->npages--;
clear:
                umem_odp->map.pfn_list[idx] &= ~HMM_PFN_FLAGS;
        }
}
EXPORT_SYMBOL(ib_umem_odp_unmap_dma_pages);