/*
 * 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/pid.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/vmalloc.h>

#include <rdma/ib_verbs.h>
#include <rdma/ib_umem.h>
#include <rdma/ib_umem_odp.h>

static void ib_umem_notifier_start_account(struct ib_umem *item)
{
        mutex_lock(&item->odp_data->umem_mutex);

        /* Only update private counters for this umem if it has them.
         * Otherwise skip it. All page faults will be delayed for this umem. */
        if (item->odp_data->mn_counters_active) {
                int notifiers_count = item->odp_data->notifiers_count++;

                if (notifiers_count == 0)
                        /* Initialize the completion object for waiting on
                         * notifiers. Since notifier_count is zero, no one
                         * should be waiting right now. */
                        reinit_completion(&item->odp_data->notifier_completion);
        }
        mutex_unlock(&item->odp_data->umem_mutex);
}

static void ib_umem_notifier_end_account(struct ib_umem *item)
{
        mutex_lock(&item->odp_data->umem_mutex);

        /* Only update private counters for this umem if it has them.
         * Otherwise skip it. All page faults will be delayed for this umem. */
        if (item->odp_data->mn_counters_active) {
                /*
                 * This sequence increase will notify the QP page fault that
                 * the page that is going to be mapped in the spte could have
                 * been freed.
                 */
                ++item->odp_data->notifiers_seq;
                if (--item->odp_data->notifiers_count == 0)
                        complete_all(&item->odp_data->notifier_completion);
        }
        mutex_unlock(&item->odp_data->umem_mutex);
}

/* Account for a new mmu notifier in an ib_ucontext. */
static void ib_ucontext_notifier_start_account(struct ib_ucontext *context)
{
        atomic_inc(&context->notifier_count);
}

/* Account for a terminating mmu notifier in an ib_ucontext.
 *
 * Must be called with the ib_ucontext->umem_rwsem semaphore unlocked, since
 * the function takes the semaphore itself. */
static void ib_ucontext_notifier_end_account(struct ib_ucontext *context)
{
        int zero_notifiers = atomic_dec_and_test(&context->notifier_count);

        if (zero_notifiers &&
            !list_empty(&context->no_private_counters)) {
                /* No currently running mmu notifiers. Now is the chance to
                 * add private accounting to all previously added umems. */
                struct ib_umem_odp *odp_data, *next;

                /* Prevent concurrent mmu notifiers from working on the
                 * no_private_counters list. */
                down_write(&context->umem_rwsem);

                /* Read the notifier_count again, with the umem_rwsem
                 * semaphore taken for write. */
                if (!atomic_read(&context->notifier_count)) {
                        list_for_each_entry_safe(odp_data, next,
                                                 &context->no_private_counters,
                                                 no_private_counters) {
                                mutex_lock(&odp_data->umem_mutex);
                                odp_data->mn_counters_active = true;
                                list_del(&odp_data->no_private_counters);
                                complete_all(&odp_data->notifier_completion);
                                mutex_unlock(&odp_data->umem_mutex);
                        }
                }

                up_write(&context->umem_rwsem);
        }
}

static int ib_umem_notifier_release_trampoline(struct ib_umem *item, u64 start,
                                               u64 end, void *cookie) {
        /*
         * Increase the number of notifiers running, to
         * prevent any further fault handling on this MR.
         */
        ib_umem_notifier_start_account(item);
        item->odp_data->dying = 1;
        /* Make sure that the fact the umem is dying is out before we release
         * all pending page faults. */
        smp_wmb();
        complete_all(&item->odp_data->notifier_completion);
        item->context->invalidate_range(item, ib_umem_start(item),
                                        ib_umem_end(item));
        return 0;
}

static void ib_umem_notifier_release(struct mmu_notifier *mn,
                                     struct mm_struct *mm)
{
        struct ib_ucontext *context = container_of(mn, struct ib_ucontext, mn);

        if (!context->invalidate_range)
                return;

        ib_ucontext_notifier_start_account(context);
        down_read(&context->umem_rwsem);
        rbt_ib_umem_for_each_in_range(&context->umem_tree, 0,
                                      ULLONG_MAX,
                                      ib_umem_notifier_release_trampoline,
                                      NULL);
        up_read(&context->umem_rwsem);
}

static int invalidate_page_trampoline(struct ib_umem *item, u64 start,
                                      u64 end, void *cookie)
{
        ib_umem_notifier_start_account(item);
        item->context->invalidate_range(item, start, start + PAGE_SIZE);
        ib_umem_notifier_end_account(item);
        return 0;
}

static void ib_umem_notifier_invalidate_page(struct mmu_notifier *mn,
                                             struct mm_struct *mm,
                                             unsigned long address)
{
        struct ib_ucontext *context = container_of(mn, struct ib_ucontext, mn);

        if (!context->invalidate_range)
                return;

        ib_ucontext_notifier_start_account(context);
        down_read(&context->umem_rwsem);
        rbt_ib_umem_for_each_in_range(&context->umem_tree, address,
                                      address + PAGE_SIZE,
                                      invalidate_page_trampoline, NULL);
        up_read(&context->umem_rwsem);
        ib_ucontext_notifier_end_account(context);
}

static int invalidate_range_start_trampoline(struct ib_umem *item, u64 start,
                                             u64 end, void *cookie)
{
        ib_umem_notifier_start_account(item);
        item->context->invalidate_range(item, start, end);
        return 0;
}

static void ib_umem_notifier_invalidate_range_start(struct mmu_notifier *mn,
                                                    struct mm_struct *mm,
                                                    unsigned long start,
                                                    unsigned long end)
{
        struct ib_ucontext *context = container_of(mn, struct ib_ucontext, mn);

        if (!context->invalidate_range)
                return;

        ib_ucontext_notifier_start_account(context);
        down_read(&context->umem_rwsem);
        rbt_ib_umem_for_each_in_range(&context->umem_tree, start,
                                      end,
                                      invalidate_range_start_trampoline, NULL);
        up_read(&context->umem_rwsem);
}

static int invalidate_range_end_trampoline(struct ib_umem *item, u64 start,
                                           u64 end, void *cookie)
{
        ib_umem_notifier_end_account(item);
        return 0;
}

static void ib_umem_notifier_invalidate_range_end(struct mmu_notifier *mn,
                                                  struct mm_struct *mm,
                                                  unsigned long start,
                                                  unsigned long end)
{
        struct ib_ucontext *context = container_of(mn, struct ib_ucontext, mn);

        if (!context->invalidate_range)
                return;

        down_read(&context->umem_rwsem);
        rbt_ib_umem_for_each_in_range(&context->umem_tree, start,
                                      end,
                                      invalidate_range_end_trampoline, NULL);
        up_read(&context->umem_rwsem);
        ib_ucontext_notifier_end_account(context);
}

static const struct mmu_notifier_ops ib_umem_notifiers = {
        .release                    = ib_umem_notifier_release,
        .invalidate_page            = ib_umem_notifier_invalidate_page,
        .invalidate_range_start     = ib_umem_notifier_invalidate_range_start,
        .invalidate_range_end       = ib_umem_notifier_invalidate_range_end,
};

int ib_umem_odp_get(struct ib_ucontext *context, struct ib_umem *umem)
{
        int ret_val;
        struct pid *our_pid;
        struct mm_struct *mm = get_task_mm(current);

        if (!mm)
                return -EINVAL;

        /* Prevent creating ODP MRs in child processes */
        rcu_read_lock();
        our_pid = get_task_pid(current->group_leader, PIDTYPE_PID);
        rcu_read_unlock();
        put_pid(our_pid);
        if (context->tgid != our_pid) {
                ret_val = -EINVAL;
                goto out_mm;
        }

        umem->hugetlb = 0;
        umem->odp_data = kzalloc(sizeof(*umem->odp_data), GFP_KERNEL);
        if (!umem->odp_data) {
                ret_val = -ENOMEM;
                goto out_mm;
        }
        umem->odp_data->umem = umem;

        mutex_init(&umem->odp_data->umem_mutex);

        init_completion(&umem->odp_data->notifier_completion);

        umem->odp_data->page_list = vzalloc(ib_umem_num_pages(umem) *
                                            sizeof(*umem->odp_data->page_list));
        if (!umem->odp_data->page_list) {
                ret_val = -ENOMEM;
                goto out_odp_data;
        }

        umem->odp_data->dma_list = vzalloc(ib_umem_num_pages(umem) *
                                          sizeof(*umem->odp_data->dma_list));
        if (!umem->odp_data->dma_list) {
                ret_val = -ENOMEM;
                goto out_page_list;
        }

        /*
         * When using MMU notifiers, we will get a
         * notification before the "current" task (and MM) is
         * destroyed. We use the umem_rwsem semaphore to synchronize.
         */
        down_write(&context->umem_rwsem);
        context->odp_mrs_count++;
        if (likely(ib_umem_start(umem) != ib_umem_end(umem)))
                rbt_ib_umem_insert(&umem->odp_data->interval_tree,
                                   &context->umem_tree);
        if (likely(!atomic_read(&context->notifier_count)) ||
            context->odp_mrs_count == 1)
                umem->odp_data->mn_counters_active = true;
        else
                list_add(&umem->odp_data->no_private_counters,
                         &context->no_private_counters);
        downgrade_write(&context->umem_rwsem);

        if (context->odp_mrs_count == 1) {
                /*
                 * Note that at this point, no MMU notifier is running
                 * for this context!
                 */
                atomic_set(&context->notifier_count, 0);
                INIT_HLIST_NODE(&context->mn.hlist);
                context->mn.ops = &ib_umem_notifiers;
                /*
                 * Lock-dep detects a false positive for mmap_sem vs.
                 * umem_rwsem, due to not grasping downgrade_write correctly.
                 */
                lockdep_off();
                ret_val = mmu_notifier_register(&context->mn, mm);
                lockdep_on();
                if (ret_val) {
                        pr_err("Failed to register mmu_notifier %d\n", ret_val);
                        ret_val = -EBUSY;
                        goto out_mutex;
                }
        }

        up_read(&context->umem_rwsem);

        /*
         * Note that doing an mmput can cause a notifier for the relevant mm.
         * If the notifier is called while we hold the umem_rwsem, this will
         * cause a deadlock. Therefore, we release the reference only after we
         * released the semaphore.
         */
        mmput(mm);
        return 0;

out_mutex:
        up_read(&context->umem_rwsem);
        vfree(umem->odp_data->dma_list);
out_page_list:
        vfree(umem->odp_data->page_list);
out_odp_data:
        kfree(umem->odp_data);
out_mm:
        mmput(mm);
        return ret_val;
}

void ib_umem_odp_release(struct ib_umem *umem)
{
        struct ib_ucontext *context = umem->context;

        /*
         * 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.
         */
        ib_umem_odp_unmap_dma_pages(umem, ib_umem_start(umem),
                                    ib_umem_end(umem));

        down_write(&context->umem_rwsem);
        if (likely(ib_umem_start(umem) != ib_umem_end(umem)))
                rbt_ib_umem_remove(&umem->odp_data->interval_tree,
                                   &context->umem_tree);
        context->odp_mrs_count--;
        if (!umem->odp_data->mn_counters_active) {
                list_del(&umem->odp_data->no_private_counters);
                complete_all(&umem->odp_data->notifier_completion);
        }

        /*
         * Downgrade the lock to a read lock. This ensures that the notifiers
         * (who lock the mutex for reading) will be able to finish, and we
         * will be able to enventually obtain the mmu notifiers SRCU. Note
         * that since we are doing it atomically, no other user could register
         * and unregister while we do the check.
         */
        downgrade_write(&context->umem_rwsem);
        if (!context->odp_mrs_count) {
                struct task_struct *owning_process = NULL;
                struct mm_struct *owning_mm        = NULL;

                owning_process = get_pid_task(context->tgid,
                                              PIDTYPE_PID);
                if (owning_process == NULL)
                        /*
                         * The process is already dead, notifier were removed
                         * already.
                         */
                        goto out;

                owning_mm = get_task_mm(owning_process);
                if (owning_mm == NULL)
                        /*
                         * The process' mm is already dead, notifier were
                         * removed already.
                         */
                        goto out_put_task;
                mmu_notifier_unregister(&context->mn, owning_mm);

                mmput(owning_mm);

out_put_task:
                put_task_struct(owning_process);
        }
out:
        up_read(&context->umem_rwsem);

        vfree(umem->odp_data->dma_list);
        vfree(umem->odp_data->page_list);
        kfree(umem->odp_data);
        kfree(umem);
}

/*
 * Map for DMA and insert a single page into the on-demand paging page tables.
 *
 * @umem: the umem to insert the page to.
 * @page_index: index in the umem to add the page to.
 * @page: the page struct to map and add.
 * @access_mask: access permissions needed for this page.
 * @current_seq: sequence number for synchronization with invalidations.
 *               the sequence number is taken from
 *               umem->odp_data->notifiers_seq.
 *
 * The function returns -EFAULT if the DMA mapping operation fails. It returns
 * -EAGAIN if a concurrent invalidation prevents us from updating the page.
 *
 * The page is released via put_page even if the operation failed. For
 * on-demand pinning, the page is released whenever it isn't stored in the
 * umem.
 */
static int ib_umem_odp_map_dma_single_page(
                struct ib_umem *umem,
                int page_index,
                u64 base_virt_addr,
                struct page *page,
                u64 access_mask,
                unsigned long current_seq)
{
        struct ib_device *dev = umem->context->device;
        dma_addr_t dma_addr;
        int stored_page = 0;
        int remove_existing_mapping = 0;
        int ret = 0;

        /*
         * Note: we avoid writing if seq is different from the initial seq, to
         * handle case of a racing notifier. This check also allows us to bail
         * early if we have a notifier running in parallel with us.
         */
        if (ib_umem_mmu_notifier_retry(umem, current_seq)) {
                ret = -EAGAIN;
                goto out;
        }
        if (!(umem->odp_data->dma_list[page_index])) {
                dma_addr = ib_dma_map_page(dev,
                                           page,
                                           0, PAGE_SIZE,
                                           DMA_BIDIRECTIONAL);
                if (ib_dma_mapping_error(dev, dma_addr)) {
                        ret = -EFAULT;
                        goto out;
                }
                umem->odp_data->dma_list[page_index] = dma_addr | access_mask;
                umem->odp_data->page_list[page_index] = page;
                stored_page = 1;
        } else if (umem->odp_data->page_list[page_index] == page) {
                umem->odp_data->dma_list[page_index] |= access_mask;
        } else {
                pr_err("error: got different pages in IB device and from get_user_pages. IB device page: %p, gup page: %p\n",
                       umem->odp_data->page_list[page_index], page);
                /* Better remove the mapping now, to prevent any further
                 * damage. */
                remove_existing_mapping = 1;
        }

out:
        /* On Demand Paging - avoid pinning the page */
        if (umem->context->invalidate_range || !stored_page)
                put_page(page);

        if (remove_existing_mapping && umem->context->invalidate_range) {
                invalidate_page_trampoline(
                        umem,
                        base_virt_addr + (page_index * PAGE_SIZE),
                        base_virt_addr + ((page_index+1)*PAGE_SIZE),
                        NULL);
                ret = -EAGAIN;
        }

        return ret;
}

/**
 * ib_umem_odp_map_dma_pages - Pin and DMA map userspace memory in an ODP MR.
 *
 * Pins the range of pages passed in the argument, and maps them to
 * DMA addresses. The DMA addresses of the mapped pages is updated in
 * umem->odp_data->dma_list.
 *
 * Returns the number of pages mapped in success, negative error code
 * for failure.
 * An -EAGAIN error code is returned when a concurrent mmu notifier prevents
 * the function from completing its task.
 *
 * @umem: 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.
 * @current_seq: the MMU notifiers sequance value for synchronization with
 *               invalidations. the sequance number is read from
 *               umem->odp_data->notifiers_seq before calling this function
 */
int ib_umem_odp_map_dma_pages(struct ib_umem *umem, u64 user_virt, u64 bcnt,
                              u64 access_mask, unsigned long current_seq)
{
        struct task_struct *owning_process  = NULL;
        struct mm_struct   *owning_mm       = NULL;
        struct page       **local_page_list = NULL;
        u64 off;
        int j, k, ret = 0, start_idx, npages = 0;
        u64 base_virt_addr;
        unsigned int flags = 0;

        if (access_mask == 0)
                return -EINVAL;

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

        local_page_list = (struct page **)__get_free_page(GFP_KERNEL);
        if (!local_page_list)
                return -ENOMEM;

        off = user_virt & (~PAGE_MASK);
        user_virt = user_virt & PAGE_MASK;
        base_virt_addr = user_virt;
        bcnt += off; /* Charge for the first page offset as well. */

        owning_process = get_pid_task(umem->context->tgid, PIDTYPE_PID);
        if (owning_process == NULL) {
                ret = -EINVAL;
                goto out_no_task;
        }

        owning_mm = get_task_mm(owning_process);
        if (owning_mm == NULL) {
                ret = -EINVAL;
                goto out_put_task;
        }

        if (access_mask & ODP_WRITE_ALLOWED_BIT)
                flags |= FOLL_WRITE;

        start_idx = (user_virt - ib_umem_start(umem)) >> PAGE_SHIFT;
        k = start_idx;

        while (bcnt > 0) {
                const size_t gup_num_pages =
                        min_t(size_t, ALIGN(bcnt, PAGE_SIZE) / PAGE_SIZE,
                              PAGE_SIZE / sizeof(struct page *));

                down_read(&owning_mm->mmap_sem);
                /*
                 * Note: this might result in redundent page getting. We can
                 * avoid this by checking dma_list to be 0 before calling
                 * get_user_pages. However, this make the code much more
                 * complex (and doesn't gain us much performance in most use
                 * cases).
                 */
                npages = get_user_pages_remote(owning_process, owning_mm,
                                user_virt, gup_num_pages,
                                flags, local_page_list, NULL, NULL);
                up_read(&owning_mm->mmap_sem);

                if (npages < 0)
                        break;

                bcnt -= min_t(size_t, npages << PAGE_SHIFT, bcnt);
                user_virt += npages << PAGE_SHIFT;
                mutex_lock(&umem->odp_data->umem_mutex);
                for (j = 0; j < npages; ++j) {
                        ret = ib_umem_odp_map_dma_single_page(
                                umem, k, base_virt_addr, local_page_list[j],
                                access_mask, current_seq);
                        if (ret < 0)
                                break;
                        k++;
                }
                mutex_unlock(&umem->odp_data->umem_mutex);

                if (ret < 0) {
                        /* Release left over pages when handling errors. */
                        for (++j; j < npages; ++j)
                                put_page(local_page_list[j]);
                        break;
                }
        }

        if (ret >= 0) {
                if (npages < 0 && k == start_idx)
                        ret = npages;
                else
                        ret = k - start_idx;
        }

        mmput(owning_mm);
out_put_task:
        put_task_struct(owning_process);
out_no_task:
        free_page((unsigned long)local_page_list);
        return ret;
}
EXPORT_SYMBOL(ib_umem_odp_map_dma_pages);

void ib_umem_odp_unmap_dma_pages(struct ib_umem *umem, u64 virt,
                                 u64 bound)
{
        int idx;
        u64 addr;
        struct ib_device *dev = umem->context->device;

        virt  = max_t(u64, virt,  ib_umem_start(umem));
        bound = min_t(u64, bound, ib_umem_end(umem));
        /* Note that during the run of this function, the
         * notifiers_count of the MR is > 0, preventing any racing
         * faults from completion. We might be racing with other
         * invalidations, so we must make sure we free each page only
         * once. */
        mutex_lock(&umem->odp_data->umem_mutex);
        for (addr = virt; addr < bound; addr += (u64)umem->page_size) {
                idx = (addr - ib_umem_start(umem)) / PAGE_SIZE;
                if (umem->odp_data->page_list[idx]) {
                        struct page *page = umem->odp_data->page_list[idx];
                        dma_addr_t dma = umem->odp_data->dma_list[idx];
                        dma_addr_t dma_addr = dma & ODP_DMA_ADDR_MASK;

                        WARN_ON(!dma_addr);

                        ib_dma_unmap_page(dev, dma_addr, PAGE_SIZE,
                                          DMA_BIDIRECTIONAL);
                        if (dma & ODP_WRITE_ALLOWED_BIT) {
                                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);
                        }
                        /* on demand pinning support */
                        if (!umem->context->invalidate_range)
                                put_page(page);
                        umem->odp_data->page_list[idx] = NULL;
                        umem->odp_data->dma_list[idx] = 0;
                }
        }
        mutex_unlock(&umem->odp_data->umem_mutex);
}
EXPORT_SYMBOL(ib_umem_odp_unmap_dma_pages);