/*
 * 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/pagemap.h>

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

#include "uverbs.h"

static void ib_umem_notifier_start_account(struct ib_umem_odp *umem_odp)
{
        mutex_lock(&umem_odp->umem_mutex);
        if (umem_odp->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(&umem_odp->notifier_completion);
        mutex_unlock(&umem_odp->umem_mutex);
}

static void ib_umem_notifier_end_account(struct ib_umem_odp *umem_odp)
{
        mutex_lock(&umem_odp->umem_mutex);
        /*
         * 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.
         */
        ++umem_odp->notifiers_seq;
        if (--umem_odp->notifiers_count == 0)
                complete_all(&umem_odp->notifier_completion);
        mutex_unlock(&umem_odp->umem_mutex);
}

static void ib_umem_notifier_release(struct mmu_notifier *mn,
                                     struct mm_struct *mm)
{
        struct ib_ucontext_per_mm *per_mm =
                container_of(mn, struct ib_ucontext_per_mm, mn);
        struct rb_node *node;

        down_read(&per_mm->umem_rwsem);
        if (!per_mm->mn.users)
                goto out;

        for (node = rb_first_cached(&per_mm->umem_tree); node;
             node = rb_next(node)) {
                struct ib_umem_odp *umem_odp =
                        rb_entry(node, struct ib_umem_odp, interval_tree.rb);

                /*
                 * Increase the number of notifiers running, to prevent any
                 * further fault handling on this MR.
                 */
                ib_umem_notifier_start_account(umem_odp);
                complete_all(&umem_odp->notifier_completion);
                umem_odp->umem.ibdev->ops.invalidate_range(
                        umem_odp, ib_umem_start(umem_odp),
                        ib_umem_end(umem_odp));
        }

out:
        up_read(&per_mm->umem_rwsem);
}

static int invalidate_range_start_trampoline(struct ib_umem_odp *item,
                                             u64 start, u64 end, void *cookie)
{
        ib_umem_notifier_start_account(item);
        item->umem.ibdev->ops.invalidate_range(item, start, end);
        return 0;
}

static int ib_umem_notifier_invalidate_range_start(struct mmu_notifier *mn,
                                const struct mmu_notifier_range *range)
{
        struct ib_ucontext_per_mm *per_mm =
                container_of(mn, struct ib_ucontext_per_mm, mn);
        int rc;

        if (mmu_notifier_range_blockable(range))
                down_read(&per_mm->umem_rwsem);
        else if (!down_read_trylock(&per_mm->umem_rwsem))
                return -EAGAIN;

        if (!per_mm->mn.users) {
                up_read(&per_mm->umem_rwsem);
                /*
                 * At this point users is permanently zero and visible to this
                 * CPU without a lock, that fact is relied on to skip the unlock
                 * in range_end.
                 */
                return 0;
        }

        rc = rbt_ib_umem_for_each_in_range(&per_mm->umem_tree, range->start,
                                           range->end,
                                           invalidate_range_start_trampoline,
                                           mmu_notifier_range_blockable(range),
                                           NULL);
        if (rc)
                up_read(&per_mm->umem_rwsem);
        return rc;
}

static int invalidate_range_end_trampoline(struct ib_umem_odp *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,
                                const struct mmu_notifier_range *range)
{
        struct ib_ucontext_per_mm *per_mm =
                container_of(mn, struct ib_ucontext_per_mm, mn);

        if (unlikely(!per_mm->mn.users))
                return;

        rbt_ib_umem_for_each_in_range(&per_mm->umem_tree, range->start,
                                      range->end,
                                      invalidate_range_end_trampoline, true, NULL);
        up_read(&per_mm->umem_rwsem);
}

static struct mmu_notifier *ib_umem_alloc_notifier(struct mm_struct *mm)
{
        struct ib_ucontext_per_mm *per_mm;

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

        per_mm->umem_tree = RB_ROOT_CACHED;
        init_rwsem(&per_mm->umem_rwsem);

        WARN_ON(mm != current->mm);
        rcu_read_lock();
        per_mm->tgid = get_task_pid(current->group_leader, PIDTYPE_PID);
        rcu_read_unlock();
        return &per_mm->mn;
}

static void ib_umem_free_notifier(struct mmu_notifier *mn)
{
        struct ib_ucontext_per_mm *per_mm =
                container_of(mn, struct ib_ucontext_per_mm, mn);

        WARN_ON(!RB_EMPTY_ROOT(&per_mm->umem_tree.rb_root));

        put_pid(per_mm->tgid);
        kfree(per_mm);
}

static const struct mmu_notifier_ops ib_umem_notifiers = {
        .release                    = ib_umem_notifier_release,
        .invalidate_range_start     = ib_umem_notifier_invalidate_range_start,
        .invalidate_range_end       = ib_umem_notifier_invalidate_range_end,
        .alloc_notifier             = ib_umem_alloc_notifier,
        .free_notifier              = ib_umem_free_notifier,
};

static inline int ib_init_umem_odp(struct ib_umem_odp *umem_odp)
{
        struct ib_ucontext_per_mm *per_mm;
        struct mmu_notifier *mn;
        int ret;

        umem_odp->umem.is_odp = 1;
        if (!umem_odp->is_implicit_odp) {
                size_t page_size = 1UL << umem_odp->page_shift;
                size_t pages;

                umem_odp->interval_tree.start =
                        ALIGN_DOWN(umem_odp->umem.address, page_size);
                if (check_add_overflow(umem_odp->umem.address,
                                       (unsigned long)umem_odp->umem.length,
                                       &umem_odp->interval_tree.last))
                        return -EOVERFLOW;
                umem_odp->interval_tree.last =
                        ALIGN(umem_odp->interval_tree.last, page_size);
                if (unlikely(umem_odp->interval_tree.last < page_size))
                        return -EOVERFLOW;

                pages = (umem_odp->interval_tree.last -
                         umem_odp->interval_tree.start) >>
                        umem_odp->page_shift;
                if (!pages)
                        return -EINVAL;

                /*
                 * Note that the representation of the intervals in the
                 * interval tree considers the ending point as contained in
                 * the interval.
                 */
                umem_odp->interval_tree.last--;

                umem_odp->page_list = kvcalloc(
                        pages, sizeof(*umem_odp->page_list), GFP_KERNEL);
                if (!umem_odp->page_list)
                        return -ENOMEM;

                umem_odp->dma_list = kvcalloc(
                        pages, sizeof(*umem_odp->dma_list), GFP_KERNEL);
                if (!umem_odp->dma_list) {
                        ret = -ENOMEM;
                        goto out_page_list;
                }
        }

        mn = mmu_notifier_get(&ib_umem_notifiers, umem_odp->umem.owning_mm);
        if (IS_ERR(mn)) {
                ret = PTR_ERR(mn);
                goto out_dma_list;
        }
        umem_odp->per_mm = per_mm =
                container_of(mn, struct ib_ucontext_per_mm, mn);

        mutex_init(&umem_odp->umem_mutex);
        init_completion(&umem_odp->notifier_completion);

        if (!umem_odp->is_implicit_odp) {
                down_write(&per_mm->umem_rwsem);
                interval_tree_insert(&umem_odp->interval_tree,
                                     &per_mm->umem_tree);
                up_write(&per_mm->umem_rwsem);
        }
        mmgrab(umem_odp->umem.owning_mm);

        return 0;

out_dma_list:
        kvfree(umem_odp->dma_list);
out_page_list:
        kvfree(umem_odp->page_list);
        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.
 *
 * @udata: udata from the syscall being used to create the umem
 * @access: ib_reg_mr access flags
 */
struct ib_umem_odp *ib_umem_odp_alloc_implicit(struct ib_udata *udata,
                                               int access)
{
        struct ib_ucontext *context =
                container_of(udata, struct uverbs_attr_bundle, driver_udata)
                        ->context;
        struct ib_umem *umem;
        struct ib_umem_odp *umem_odp;
        int ret;

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

        if (!context)
                return ERR_PTR(-EIO);
        if (WARN_ON_ONCE(!context->device->ops.invalidate_range))
                return ERR_PTR(-EINVAL);

        umem_odp = kzalloc(sizeof(*umem_odp), GFP_KERNEL);
        if (!umem_odp)
                return ERR_PTR(-ENOMEM);
        umem = &umem_odp->umem;
        umem->ibdev = context->device;
        umem->writable = ib_access_writable(access);
        umem->owning_mm = current->mm;
        umem_odp->is_implicit_odp = 1;
        umem_odp->page_shift = PAGE_SHIFT;

        ret = ib_init_umem_odp(umem_odp);
        if (ret) {
                kfree(umem_odp);
                return ERR_PTR(ret);
        }
        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
 */
struct ib_umem_odp *ib_umem_odp_alloc_child(struct ib_umem_odp *root,
                                            unsigned long addr, size_t size)
{
        /*
         * 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(sizeof(*odp_data), GFP_KERNEL);
        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;

        ret = ib_init_umem_odp(odp_data);
        if (ret) {
                kfree(odp_data);
                return ERR_PTR(ret);
        }
        return odp_data;
}
EXPORT_SYMBOL(ib_umem_odp_alloc_child);

/**
 * ib_umem_odp_get - Create a umem_odp for a userspace va
 *
 * @udata: 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
 *
 * 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_udata *udata, unsigned long addr,
                                    size_t size, int access)
{
        struct ib_umem_odp *umem_odp;
        struct ib_ucontext *context;
        struct mm_struct *mm;
        int ret;

        if (!udata)
                return ERR_PTR(-EIO);

        context = container_of(udata, struct uverbs_attr_bundle, driver_udata)
                          ->context;
        if (!context)
                return ERR_PTR(-EIO);

        if (WARN_ON_ONCE(!(access & IB_ACCESS_ON_DEMAND)) ||
            WARN_ON_ONCE(!context->device->ops.invalidate_range))
                return ERR_PTR(-EINVAL);

        umem_odp = kzalloc(sizeof(struct ib_umem_odp), GFP_KERNEL);
        if (!umem_odp)
                return ERR_PTR(-ENOMEM);

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

        umem_odp->page_shift = PAGE_SHIFT;
        if (access & IB_ACCESS_HUGETLB) {
                struct vm_area_struct *vma;
                struct hstate *h;

                down_read(&mm->mmap_sem);
                vma = find_vma(mm, ib_umem_start(umem_odp));
                if (!vma || !is_vm_hugetlb_page(vma)) {
                        up_read(&mm->mmap_sem);
                        ret = -EINVAL;
                        goto err_free;
                }
                h = hstate_vma(vma);
                umem_odp->page_shift = huge_page_shift(h);
                up_read(&mm->mmap_sem);
        }

        ret = ib_init_umem_odp(umem_odp);
        if (ret)
                goto err_free;
        return umem_odp;

err_free:
        kfree(umem_odp);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL(ib_umem_odp_get);

void ib_umem_odp_release(struct ib_umem_odp *umem_odp)
{
        struct ib_ucontext_per_mm *per_mm = umem_odp->per_mm;

        /*
         * 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.
         */
        if (!umem_odp->is_implicit_odp) {
                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);
                kvfree(umem_odp->dma_list);
                kvfree(umem_odp->page_list);
        }

        down_write(&per_mm->umem_rwsem);
        if (!umem_odp->is_implicit_odp) {
                interval_tree_remove(&umem_odp->interval_tree,
                                     &per_mm->umem_tree);
                complete_all(&umem_odp->notifier_completion);
        }
        /*
         * NOTE! mmu_notifier_unregister() can happen between a start/end
         * callback, resulting in a missing end, and thus an unbalanced
         * lock. This doesn't really matter to us since we are about to kfree
         * the memory that holds the lock, however LOCKDEP doesn't like this.
         * Thus we call the mmu_notifier_put under the rwsem and test the
         * internal users count to reliably see if we are past this point.
         */
        mmu_notifier_put(&per_mm->mn);
        up_write(&per_mm->umem_rwsem);

        mmdrop(umem_odp->umem.owning_mm);
        kfree(umem_odp);
}
EXPORT_SYMBOL(ib_umem_odp_release);

/*
 * 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->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_user_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_odp *umem_odp,
                int page_index,
                struct page *page,
                u64 access_mask,
                unsigned long current_seq)
{
        struct ib_device *dev = umem_odp->umem.ibdev;
        dma_addr_t dma_addr;
        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_odp, current_seq)) {
                ret = -EAGAIN;
                goto out;
        }
        if (!(umem_odp->dma_list[page_index])) {
                dma_addr =
                        ib_dma_map_page(dev, page, 0, BIT(umem_odp->page_shift),
                                        DMA_BIDIRECTIONAL);
                if (ib_dma_mapping_error(dev, dma_addr)) {
                        ret = -EFAULT;
                        goto out;
                }
                umem_odp->dma_list[page_index] = dma_addr | access_mask;
                umem_odp->page_list[page_index] = page;
                umem_odp->npages++;
        } else if (umem_odp->page_list[page_index] == page) {
                umem_odp->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->page_list[page_index], page);
                /* Better remove the mapping now, to prevent any further
                 * damage. */
                remove_existing_mapping = 1;
        }

out:
        put_user_page(page);

        if (remove_existing_mapping) {
                ib_umem_notifier_start_account(umem_odp);
                dev->ops.invalidate_range(
                        umem_odp,
                        ib_umem_start(umem_odp) +
                                (page_index << umem_odp->page_shift),
                        ib_umem_start(umem_odp) +
                                ((page_index + 1) << umem_odp->page_shift));
                ib_umem_notifier_end_account(umem_odp);
                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->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.
 * An -ENOENT error code indicates that userspace process is being terminated
 * and mm was already destroyed.
 * @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.
 * @current_seq: the MMU notifiers sequance value for synchronization with
 *               invalidations. the sequance number is read from
 *               umem_odp->notifiers_seq before calling this function
 */
int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt,
                              u64 bcnt, u64 access_mask,
                              unsigned long current_seq)
{
        struct task_struct *owning_process  = NULL;
        struct mm_struct *owning_mm = umem_odp->umem.owning_mm;
        struct page       **local_page_list = NULL;
        u64 page_mask, off;
        int j, k, ret = 0, start_idx, npages = 0;
        unsigned int flags = 0, page_shift;
        phys_addr_t p = 0;

        if (access_mask == 0)
                return -EINVAL;

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

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

        page_shift = umem_odp->page_shift;
        page_mask = ~(BIT(page_shift) - 1);
        off = user_virt & (~page_mask);
        user_virt = user_virt & page_mask;
        bcnt += off; /* Charge for the first page offset as well. */

        /*
         * 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->per_mm->tgid, PIDTYPE_PID);
        if (!owning_process || !mmget_not_zero(owning_mm)) {
                ret = -EINVAL;
                goto out_put_task;
        }

        if (access_mask & ODP_WRITE_ALLOWED_BIT)
                flags |= FOLL_WRITE;

        start_idx = (user_virt - ib_umem_start(umem_odp)) >> page_shift;
        k = start_idx;

        while (bcnt > 0) {
                const size_t gup_num_pages = min_t(size_t,
                                (bcnt + BIT(page_shift) - 1) >> page_shift,
                                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) {
                        if (npages != -EAGAIN)
                                pr_warn("fail to get %zu user pages with error %d\n", gup_num_pages, npages);
                        else
                                pr_debug("fail to get %zu user pages with error %d\n", gup_num_pages, npages);
                        break;
                }

                bcnt -= min_t(size_t, npages << PAGE_SHIFT, bcnt);
                mutex_lock(&umem_odp->umem_mutex);
                for (j = 0; j < npages; j++, user_virt += PAGE_SIZE) {
                        if (user_virt & ~page_mask) {
                                p += PAGE_SIZE;
                                if (page_to_phys(local_page_list[j]) != p) {
                                        ret = -EFAULT;
                                        break;
                                }
                                put_user_page(local_page_list[j]);
                                continue;
                        }

                        ret = ib_umem_odp_map_dma_single_page(
                                        umem_odp, k, local_page_list[j],
                                        access_mask, current_seq);
                        if (ret < 0) {
                                if (ret != -EAGAIN)
                                        pr_warn("ib_umem_odp_map_dma_single_page failed with error %d\n", ret);
                                else
                                        pr_debug("ib_umem_odp_map_dma_single_page failed with error %d\n", ret);
                                break;
                        }

                        p = page_to_phys(local_page_list[j]);
                        k++;
                }
                mutex_unlock(&umem_odp->umem_mutex);

                if (ret < 0) {
                        /*
                         * Release pages, remembering that the first page
                         * to hit an error was already released by
                         * ib_umem_odp_map_dma_single_page().
                         */
                        if (npages - (j + 1) > 0)
                                put_user_pages(&local_page_list[j+1],
                                               npages - (j + 1));
                        break;
                }
        }

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

        mmput(owning_mm);
out_put_task:
        if (owning_process)
                put_task_struct(owning_process);
        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_odp *umem_odp, u64 virt,
                                 u64 bound)
{
        int idx;
        u64 addr;
        struct ib_device *dev = umem_odp->umem.ibdev;

        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));
        /* 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. */
        for (addr = virt; addr < bound; addr += BIT(umem_odp->page_shift)) {
                idx = (addr - ib_umem_start(umem_odp)) >> umem_odp->page_shift;
                if (umem_odp->page_list[idx]) {
                        struct page *page = umem_odp->page_list[idx];
                        dma_addr_t dma = umem_odp->dma_list[idx];
                        dma_addr_t dma_addr = dma & ODP_DMA_ADDR_MASK;

                        WARN_ON(!dma_addr);

                        ib_dma_unmap_page(dev, dma_addr,
                                          BIT(umem_odp->page_shift),
                                          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);
                        }
                        umem_odp->page_list[idx] = NULL;
                        umem_odp->dma_list[idx] = 0;
                        umem_odp->npages--;
                }
        }
}
EXPORT_SYMBOL(ib_umem_odp_unmap_dma_pages);

/* @last is not a part of the interval. See comment for function
 * node_last.
 */
int rbt_ib_umem_for_each_in_range(struct rb_root_cached *root,
                                  u64 start, u64 last,
                                  umem_call_back cb,
                                  bool blockable,
                                  void *cookie)
{
        int ret_val = 0;
        struct interval_tree_node *node, *next;
        struct ib_umem_odp *umem;

        if (unlikely(start == last))
                return ret_val;

        for (node = interval_tree_iter_first(root, start, last - 1);
                        node; node = next) {
                /* TODO move the blockable decision up to the callback */
                if (!blockable)
                        return -EAGAIN;
                next = interval_tree_iter_next(node, start, last - 1);
                umem = container_of(node, struct ib_umem_odp, interval_tree);
                ret_val = cb(umem, start, last, cookie) || ret_val;
        }

        return ret_val;
}