/*

   * 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(offsetof(typeof(*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);