/*
 * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
 *
 * Based on bo.c which bears the following copyright notice,
 * but is dual licensed:
 *
 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * 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 NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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.
 *
 **************************************************************************/
/*
 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
 */

#include <linux/dma-resv.h>
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/mmu_notifier.h>

/**
 * DOC: Reservation Object Overview
 *
 * The reservation object provides a mechanism to manage shared and
 * exclusive fences associated with a buffer.  A reservation object
 * can have attached one exclusive fence (normally associated with
 * write operations) or N shared fences (read operations).  The RCU
 * mechanism is used to protect read access to fences from locked
 * write-side updates.
 */

DEFINE_WD_CLASS(reservation_ww_class);
EXPORT_SYMBOL(reservation_ww_class);

/**
 * dma_resv_list_alloc - allocate fence list
 * @shared_max: number of fences we need space for
 *
 * Allocate a new dma_resv_list and make sure to correctly initialize
 * shared_max.
 */
static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
{
        struct dma_resv_list *list;

        list = kmalloc(struct_size(list, shared, shared_max), GFP_KERNEL);
        if (!list)
                return NULL;

        list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
                sizeof(*list->shared);

        return list;
}

/**
 * dma_resv_list_free - free fence list
 * @list: list to free
 *
 * Free a dma_resv_list and make sure to drop all references.
 */
static void dma_resv_list_free(struct dma_resv_list *list)
{
        unsigned int i;

        if (!list)
                return;

        for (i = 0; i < list->shared_count; ++i)
                dma_fence_put(rcu_dereference_protected(list->shared[i], true));

        kfree_rcu(list, rcu);
}

#if IS_ENABLED(CONFIG_LOCKDEP)
static int __init dma_resv_lockdep(void)
{
        struct mm_struct *mm = mm_alloc();
        struct ww_acquire_ctx ctx;
        struct dma_resv obj;
        struct address_space mapping;
        int ret;

        if (!mm)
                return -ENOMEM;

        dma_resv_init(&obj);
        address_space_init_once(&mapping);

        mmap_read_lock(mm);
        ww_acquire_init(&ctx, &reservation_ww_class);
        ret = dma_resv_lock(&obj, &ctx);
        if (ret == -EDEADLK)
                dma_resv_lock_slow(&obj, &ctx);
        fs_reclaim_acquire(GFP_KERNEL);
        /* for unmap_mapping_range on trylocked buffer objects in shrinkers */
        i_mmap_lock_write(&mapping);
        i_mmap_unlock_write(&mapping);
#ifdef CONFIG_MMU_NOTIFIER
        lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
        __dma_fence_might_wait();
        lock_map_release(&__mmu_notifier_invalidate_range_start_map);
#else
        __dma_fence_might_wait();
#endif
        fs_reclaim_release(GFP_KERNEL);
        ww_mutex_unlock(&obj.lock);
        ww_acquire_fini(&ctx);
        mmap_read_unlock(mm);
        
        mmput(mm);

        return 0;
}
subsys_initcall(dma_resv_lockdep);
#endif

/**
 * dma_resv_init - initialize a reservation object
 * @obj: the reservation object
 */
void dma_resv_init(struct dma_resv *obj)
{
        ww_mutex_init(&obj->lock, &reservation_ww_class);
        seqcount_ww_mutex_init(&obj->seq, &obj->lock);

        RCU_INIT_POINTER(obj->fence, NULL);
        RCU_INIT_POINTER(obj->fence_excl, NULL);
}
EXPORT_SYMBOL(dma_resv_init);

/**
 * dma_resv_fini - destroys a reservation object
 * @obj: the reservation object
 */
void dma_resv_fini(struct dma_resv *obj)
{
        struct dma_resv_list *fobj;
        struct dma_fence *excl;

        /*
         * This object should be dead and all references must have
         * been released to it, so no need to be protected with rcu.
         */
        excl = rcu_dereference_protected(obj->fence_excl, 1);
        if (excl)
                dma_fence_put(excl);

        fobj = rcu_dereference_protected(obj->fence, 1);
        dma_resv_list_free(fobj);
        ww_mutex_destroy(&obj->lock);
}
EXPORT_SYMBOL(dma_resv_fini);

/**
 * dma_resv_reserve_shared - Reserve space to add shared fences to
 * a dma_resv.
 * @obj: reservation object
 * @num_fences: number of fences we want to add
 *
 * Should be called before dma_resv_add_shared_fence().  Must
 * be called with obj->lock held.
 *
 * RETURNS
 * Zero for success, or -errno
 */
int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
{
        struct dma_resv_list *old, *new;
        unsigned int i, j, k, max;

        dma_resv_assert_held(obj);

        old = dma_resv_get_list(obj);

        if (old && old->shared_max) {
                if ((old->shared_count + num_fences) <= old->shared_max)
                        return 0;
                else
                        max = max(old->shared_count + num_fences,
                                  old->shared_max * 2);
        } else {
                max = max(4ul, roundup_pow_of_two(num_fences));
        }

        new = dma_resv_list_alloc(max);
        if (!new)
                return -ENOMEM;

        /*
         * no need to bump fence refcounts, rcu_read access
         * requires the use of kref_get_unless_zero, and the
         * references from the old struct are carried over to
         * the new.
         */
        for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
                struct dma_fence *fence;

                fence = rcu_dereference_protected(old->shared[i],
                                                  dma_resv_held(obj));
                if (dma_fence_is_signaled(fence))
                        RCU_INIT_POINTER(new->shared[--k], fence);
                else
                        RCU_INIT_POINTER(new->shared[j++], fence);
        }
        new->shared_count = j;

        /*
         * We are not changing the effective set of fences here so can
         * merely update the pointer to the new array; both existing
         * readers and new readers will see exactly the same set of
         * active (unsignaled) shared fences. Individual fences and the
         * old array are protected by RCU and so will not vanish under
         * the gaze of the rcu_read_lock() readers.
         */
        rcu_assign_pointer(obj->fence, new);

        if (!old)
                return 0;

        /* Drop the references to the signaled fences */
        for (i = k; i < max; ++i) {
                struct dma_fence *fence;

                fence = rcu_dereference_protected(new->shared[i],
                                                  dma_resv_held(obj));
                dma_fence_put(fence);
        }
        kfree_rcu(old, rcu);

        return 0;
}
EXPORT_SYMBOL(dma_resv_reserve_shared);

/**
 * dma_resv_add_shared_fence - Add a fence to a shared slot
 * @obj: the reservation object
 * @fence: the shared fence to add
 *
 * Add a fence to a shared slot, obj->lock must be held, and
 * dma_resv_reserve_shared() has been called.
 */
void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
{
        struct dma_resv_list *fobj;
        struct dma_fence *old;
        unsigned int i, count;

        dma_fence_get(fence);

        dma_resv_assert_held(obj);

        fobj = dma_resv_get_list(obj);
        count = fobj->shared_count;

        write_seqcount_begin(&obj->seq);

        for (i = 0; i < count; ++i) {

                old = rcu_dereference_protected(fobj->shared[i],
                                                dma_resv_held(obj));
                if (old->context == fence->context ||
                    dma_fence_is_signaled(old))
                        goto replace;
        }

        BUG_ON(fobj->shared_count >= fobj->shared_max);
        old = NULL;
        count++;

replace:
        RCU_INIT_POINTER(fobj->shared[i], fence);
        /* pointer update must be visible before we extend the shared_count */
        smp_store_mb(fobj->shared_count, count);

        write_seqcount_end(&obj->seq);
        dma_fence_put(old);
}
EXPORT_SYMBOL(dma_resv_add_shared_fence);

/**
 * dma_resv_add_excl_fence - Add an exclusive fence.
 * @obj: the reservation object
 * @fence: the shared fence to add
 *
 * Add a fence to the exclusive slot.  The obj->lock must be held.
 */
void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
{
        struct dma_fence *old_fence = dma_resv_get_excl(obj);
        struct dma_resv_list *old;
        u32 i = 0;

        dma_resv_assert_held(obj);

        old = dma_resv_get_list(obj);
        if (old)
                i = old->shared_count;

        if (fence)
                dma_fence_get(fence);

        write_seqcount_begin(&obj->seq);
        /* write_seqcount_begin provides the necessary memory barrier */
        RCU_INIT_POINTER(obj->fence_excl, fence);
        if (old)
                old->shared_count = 0;
        write_seqcount_end(&obj->seq);

        /* inplace update, no shared fences */
        while (i--)
                dma_fence_put(rcu_dereference_protected(old->shared[i],
                                                dma_resv_held(obj)));

        dma_fence_put(old_fence);
}
EXPORT_SYMBOL(dma_resv_add_excl_fence);

/**
* dma_resv_copy_fences - Copy all fences from src to dst.
* @dst: the destination reservation object
* @src: the source reservation object
*
* Copy all fences from src to dst. dst-lock must be held.
*/
int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
{
        struct dma_resv_list *src_list, *dst_list;
        struct dma_fence *old, *new;
        unsigned i;

        dma_resv_assert_held(dst);

        rcu_read_lock();
        src_list = rcu_dereference(src->fence);

retry:
        if (src_list) {
                unsigned shared_count = src_list->shared_count;

                rcu_read_unlock();

                dst_list = dma_resv_list_alloc(shared_count);
                if (!dst_list)
                        return -ENOMEM;

                rcu_read_lock();
                src_list = rcu_dereference(src->fence);
                if (!src_list || src_list->shared_count > shared_count) {
                        kfree(dst_list);
                        goto retry;
                }

                dst_list->shared_count = 0;
                for (i = 0; i < src_list->shared_count; ++i) {
                        struct dma_fence *fence;

                        fence = rcu_dereference(src_list->shared[i]);
                        if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
                                     &fence->flags))
                                continue;

                        if (!dma_fence_get_rcu(fence)) {
                                dma_resv_list_free(dst_list);
                                src_list = rcu_dereference(src->fence);
                                goto retry;
                        }

                        if (dma_fence_is_signaled(fence)) {
                                dma_fence_put(fence);
                                continue;
                        }

                        rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
                }
        } else {
                dst_list = NULL;
        }

        new = dma_fence_get_rcu_safe(&src->fence_excl);
        rcu_read_unlock();

        src_list = dma_resv_get_list(dst);
        old = dma_resv_get_excl(dst);

        write_seqcount_begin(&dst->seq);
        /* write_seqcount_begin provides the necessary memory barrier */
        RCU_INIT_POINTER(dst->fence_excl, new);
        RCU_INIT_POINTER(dst->fence, dst_list);
        write_seqcount_end(&dst->seq);

        dma_resv_list_free(src_list);
        dma_fence_put(old);

        return 0;
}
EXPORT_SYMBOL(dma_resv_copy_fences);

/**
 * dma_resv_get_fences_rcu - Get an object's shared and exclusive
 * fences without update side lock held
 * @obj: the reservation object
 * @pfence_excl: the returned exclusive fence (or NULL)
 * @pshared_count: the number of shared fences returned
 * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
 * the required size, and must be freed by caller)
 *
 * Retrieve all fences from the reservation object. If the pointer for the
 * exclusive fence is not specified the fence is put into the array of the
 * shared fences as well. Returns either zero or -ENOMEM.
 */
int dma_resv_get_fences_rcu(struct dma_resv *obj,
                            struct dma_fence **pfence_excl,
                            unsigned *pshared_count,
                            struct dma_fence ***pshared)
{
        struct dma_fence **shared = NULL;
        struct dma_fence *fence_excl;
        unsigned int shared_count;
        int ret = 1;

        do {
                struct dma_resv_list *fobj;
                unsigned int i, seq;
                size_t sz = 0;

                shared_count = i = 0;

                rcu_read_lock();
                seq = read_seqcount_begin(&obj->seq);

                fence_excl = rcu_dereference(obj->fence_excl);
                if (fence_excl && !dma_fence_get_rcu(fence_excl))
                        goto unlock;

                fobj = rcu_dereference(obj->fence);
                if (fobj)
                        sz += sizeof(*shared) * fobj->shared_max;

                if (!pfence_excl && fence_excl)
                        sz += sizeof(*shared);

                if (sz) {
                        struct dma_fence **nshared;

                        nshared = krealloc(shared, sz,
                                           GFP_NOWAIT | __GFP_NOWARN);
                        if (!nshared) {
                                rcu_read_unlock();

                                dma_fence_put(fence_excl);
                                fence_excl = NULL;

                                nshared = krealloc(shared, sz, GFP_KERNEL);
                                if (nshared) {
                                        shared = nshared;
                                        continue;
                                }

                                ret = -ENOMEM;
                                break;
                        }
                        shared = nshared;
                        shared_count = fobj ? fobj->shared_count : 0;
                        for (i = 0; i < shared_count; ++i) {
                                shared[i] = rcu_dereference(fobj->shared[i]);
                                if (!dma_fence_get_rcu(shared[i]))
                                        break;
                        }
                }

                if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
                        while (i--)
                                dma_fence_put(shared[i]);
                        dma_fence_put(fence_excl);
                        goto unlock;
                }

                ret = 0;
unlock:
                rcu_read_unlock();
        } while (ret);

        if (pfence_excl)
                *pfence_excl = fence_excl;
        else if (fence_excl)
                shared[shared_count++] = fence_excl;

        if (!shared_count) {
                kfree(shared);
                shared = NULL;
        }

        *pshared_count = shared_count;
        *pshared = shared;
        return ret;
}
EXPORT_SYMBOL_GPL(dma_resv_get_fences_rcu);

/**
 * dma_resv_wait_timeout_rcu - Wait on reservation's objects
 * shared and/or exclusive fences.
 * @obj: the reservation object
 * @wait_all: if true, wait on all fences, else wait on just exclusive fence
 * @intr: if true, do interruptible wait
 * @timeout: timeout value in jiffies or zero to return immediately
 *
 * RETURNS
 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
 * greater than zer on success.
 */
long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
                               bool wait_all, bool intr,
                               unsigned long timeout)
{
        struct dma_fence *fence;
        unsigned seq, shared_count;
        long ret = timeout ? timeout : 1;
        int i;

retry:
        shared_count = 0;
        seq = read_seqcount_begin(&obj->seq);
        rcu_read_lock();
        i = -1;

        fence = rcu_dereference(obj->fence_excl);
        if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
                if (!dma_fence_get_rcu(fence))
                        goto unlock_retry;

                if (dma_fence_is_signaled(fence)) {
                        dma_fence_put(fence);
                        fence = NULL;
                }

        } else {
                fence = NULL;
        }

        if (wait_all) {
                struct dma_resv_list *fobj = rcu_dereference(obj->fence);

                if (fobj)
                        shared_count = fobj->shared_count;

                for (i = 0; !fence && i < shared_count; ++i) {
                        struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);

                        if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
                                     &lfence->flags))
                                continue;

                        if (!dma_fence_get_rcu(lfence))
                                goto unlock_retry;

                        if (dma_fence_is_signaled(lfence)) {
                                dma_fence_put(lfence);
                                continue;
                        }

                        fence = lfence;
                        break;
                }
        }

        rcu_read_unlock();
        if (fence) {
                if (read_seqcount_retry(&obj->seq, seq)) {
                        dma_fence_put(fence);
                        goto retry;
                }

                ret = dma_fence_wait_timeout(fence, intr, ret);
                dma_fence_put(fence);
                if (ret > 0 && wait_all && (i + 1 < shared_count))
                        goto retry;
        }
        return ret;

unlock_retry:
        rcu_read_unlock();
        goto retry;
}
EXPORT_SYMBOL_GPL(dma_resv_wait_timeout_rcu);


static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
{
        struct dma_fence *fence, *lfence = passed_fence;
        int ret = 1;

        if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
                fence = dma_fence_get_rcu(lfence);
                if (!fence)
                        return -1;

                ret = !!dma_fence_is_signaled(fence);
                dma_fence_put(fence);
        }
        return ret;
}

/**
 * dma_resv_test_signaled_rcu - Test if a reservation object's
 * fences have been signaled.
 * @obj: the reservation object
 * @test_all: if true, test all fences, otherwise only test the exclusive
 * fence
 *
 * RETURNS
 * true if all fences signaled, else false
 */
bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
{
        unsigned seq, shared_count;
        int ret;

        rcu_read_lock();
retry:
        ret = true;
        shared_count = 0;
        seq = read_seqcount_begin(&obj->seq);

        if (test_all) {
                unsigned i;

                struct dma_resv_list *fobj = rcu_dereference(obj->fence);

                if (fobj)
                        shared_count = fobj->shared_count;

                for (i = 0; i < shared_count; ++i) {
                        struct dma_fence *fence = rcu_dereference(fobj->shared[i]);

                        ret = dma_resv_test_signaled_single(fence);
                        if (ret < 0)
                                goto retry;
                        else if (!ret)
                                break;
                }

                if (read_seqcount_retry(&obj->seq, seq))
                        goto retry;
        }

        if (!shared_count) {
                struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);

                if (fence_excl) {
                        ret = dma_resv_test_signaled_single(fence_excl);
                        if (ret < 0)
                                goto retry;

                        if (read_seqcount_retry(&obj->seq, seq))
                                goto retry;
                }
        }

        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(dma_resv_test_signaled_rcu);