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Rev 4560 Rev 6084
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 * optimized for alloc/free calls, not lookups. Hence, we use an rb-tree to
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 * optimized for alloc/free calls, not lookups. Hence, we use an rb-tree to
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 * speed up offset lookups.
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 * speed up offset lookups.
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 *
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 *
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 * You must not use multiple offset managers on a single address_space.
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 * You must not use multiple offset managers on a single address_space.
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 * Otherwise, mm-core will be unable to tear down memory mappings as the VM will
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 * Otherwise, mm-core will be unable to tear down memory mappings as the VM will
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 * no longer be linear. Please use VM_NONLINEAR in that case and implement your
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 * own offset managers.
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 * no longer be linear.
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 *
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 *
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 * This offset manager works on page-based addresses. That is, every argument
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 * This offset manager works on page-based addresses. That is, every argument
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 * and return code (with the exception of drm_vma_node_offset_addr()) is given
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 * and return code (with the exception of drm_vma_node_offset_addr()) is given
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 * in number of pages, not number of bytes. That means, object sizes and offsets
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 * in number of pages, not number of bytes. That means, object sizes and offsets
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 * must always be page-aligned (as usual).
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 * must always be page-aligned (as usual).
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	write_unlock(&mgr->vm_lock);
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	write_unlock(&mgr->vm_lock);
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}
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}
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EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
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EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
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/**
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/**
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 * drm_vma_offset_lookup() - Find node in offset space
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 * drm_vma_offset_lookup_locked() - Find node in offset space
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 * @mgr: Manager object
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 * @mgr: Manager object
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 * @start: Start address for object (page-based)
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 * @start: Start address for object (page-based)
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 * @pages: Size of object (page-based)
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 * @pages: Size of object (page-based)
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 *
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 *
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 * Find a node given a start address and object size. This returns the _best_
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 * Find a node given a start address and object size. This returns the _best_
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 * match for the given node. That is, @start may point somewhere into a valid
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 * match for the given node. That is, @start may point somewhere into a valid
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 * region and the given node will be returned, as long as the node spans the
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 * region and the given node will be returned, as long as the node spans the
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 * whole requested area (given the size in number of pages as @pages).
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 * whole requested area (given the size in number of pages as @pages).
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 *
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 * Note that before lookup the vma offset manager lookup lock must be acquired
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 * with drm_vma_offset_lock_lookup(). See there for an example. This can then be
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 * used to implement weakly referenced lookups using kref_get_unless_zero().
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 *
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 * Example:
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 *     drm_vma_offset_lock_lookup(mgr);
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 *     node = drm_vma_offset_lookup_locked(mgr);
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 *     if (node)
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 *         kref_get_unless_zero(container_of(node, sth, entr));
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 *     drm_vma_offset_unlock_lookup(mgr);
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 *
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 *
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 * RETURNS:
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 * RETURNS:
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 * Returns NULL if no suitable node can be found. Otherwise, the best match
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 * Returns NULL if no suitable node can be found. Otherwise, the best match
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 * is returned. It's the caller's responsibility to make sure the node doesn't
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 * is returned. It's the caller's responsibility to make sure the node doesn't
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 * get destroyed before the caller can access it.
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 * get destroyed before the caller can access it.
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 */
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struct drm_vma_offset_node *drm_vma_offset_lookup(struct drm_vma_offset_manager *mgr,
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						  unsigned long start,
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						  unsigned long pages)
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{
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	struct drm_vma_offset_node *node;
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	read_lock(&mgr->vm_lock);
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	node = drm_vma_offset_lookup_locked(mgr, start, pages);
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	read_unlock(&mgr->vm_lock);
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	return node;
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}
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EXPORT_SYMBOL(drm_vma_offset_lookup);
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/**
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 * drm_vma_offset_lookup_locked() - Find node in offset space
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 * @mgr: Manager object
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 * @start: Start address for object (page-based)
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 * @pages: Size of object (page-based)
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 *
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 * Same as drm_vma_offset_lookup() but requires the caller to lock offset lookup
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 * manually. See drm_vma_offset_lock_lookup() for an example.
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 *
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 * RETURNS:
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 * Returns NULL if no suitable node can be found. Otherwise, the best match
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 * is returned.
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 */
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 */
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struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
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struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,
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							 unsigned long start,
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							 unsigned long start,
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							 unsigned long pages)
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							 unsigned long pages)
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{
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{