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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /**************************************************************************
  *
  * Copyright 2006 Tungsten Graphics, Inc., Bismarck, ND., USA.
  * Copyright 2016 Intel Corporation
  * 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.
  *
  *
  **************************************************************************/
 
 /*
  * Generic simple memory manager implementation. Intended to be used as a base
  * class implementation for more advanced memory managers.
  *
  * Note that the algorithm used is quite simple and there might be substantial
  * performance gains if a smarter free list is implemented. Currently it is
  * just an unordered stack of free regions. This could easily be improved if
  * an RB-tree is used instead. At least if we expect heavy fragmentation.
  *
  * Aligned allocations can also see improvement.
  *
  * Authors:
  * Thomas Hellström <thomas-at-tungstengraphics-dot-com>
  */
 
 #include <linux/export.h>
 #include <linux/interval_tree_generic.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/stacktrace.h>
 
 #include <drm/drm_mm.h>
 
 /**
  * DOC: Overview
  *
  * drm_mm provides a simple range allocator. The drivers are free to use the
  * resource allocator from the linux core if it suits them, the upside of drm_mm
  * is that it's in the DRM core. Which means that it's easier to extend for
  * some of the crazier special purpose needs of gpus.
  *
  * The main data struct is &drm_mm, allocations are tracked in &drm_mm_node.
  * Drivers are free to embed either of them into their own suitable
  * datastructures. drm_mm itself will not do any memory allocations of its own,
  * so if drivers choose not to embed nodes they need to still allocate them
  * themselves.
  *
  * The range allocator also supports reservation of preallocated blocks. This is
  * useful for taking over initial mode setting configurations from the firmware,
  * where an object needs to be created which exactly matches the firmware's
  * scanout target. As long as the range is still free it can be inserted anytime
  * after the allocator is initialized, which helps with avoiding looped
  * dependencies in the driver load sequence.
  *
  * drm_mm maintains a stack of most recently freed holes, which of all
  * simplistic datastructures seems to be a fairly decent approach to clustering
  * allocations and avoiding too much fragmentation. This means free space
  * searches are O(num_holes). Given that all the fancy features drm_mm supports
  * something better would be fairly complex and since gfx thrashing is a fairly
  * steep cliff not a real concern. Removing a node again is O(1).
  *
  * drm_mm supports a few features: Alignment and range restrictions can be
  * supplied. Furthermore every &drm_mm_node has a color value (which is just an
  * opaque unsigned long) which in conjunction with a driver callback can be used
  * to implement sophisticated placement restrictions. The i915 DRM driver uses
  * this to implement guard pages between incompatible caching domains in the
  * graphics TT.
  *
  * Two behaviors are supported for searching and allocating: bottom-up and
  * top-down. The default is bottom-up. Top-down allocation can be used if the
  * memory area has different restrictions, or just to reduce fragmentation.
  *
  * Finally iteration helpers to walk all nodes and all holes are provided as are
  * some basic allocator dumpers for debugging.
  *
  * Note that this range allocator is not thread-safe, drivers need to protect
  * modifications with their own locking. The idea behind this is that for a full
  * memory manager additional data needs to be protected anyway, hence internal
  * locking would be fully redundant.
  */
 
 #ifdef CONFIG_DRM_DEBUG_MM
 #include <linux/stackdepot.h>
 
 #define STACKDEPTH 32
 #define BUFSZ 4096
 
 static noinline void save_stack(struct drm_mm_node *node)
 {
     unsigned long entries[STACKDEPTH];
     unsigned int n;
 
     n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
 
     /* May be called under spinlock, so avoid sleeping */
     node->stack = stack_depot_save(entries, n, GFP_NOWAIT);
 }
 
 static void show_leaks(struct drm_mm *mm)
 {
     struct drm_mm_node *node;
     char *buf;
 
     buf = kmalloc(BUFSZ, GFP_KERNEL);
     if (!buf)
         return;
 
     list_for_each_entry(node, drm_mm_nodes(mm), node_list) {
         if (!node->stack) {
             DRM_ERROR("node [%08llx + %08llx]: unknown owner\n",
                   node->start, node->size);
             continue;
         }
 
         stack_depot_snprint(node->stack, buf, BUFSZ, 0);
         DRM_ERROR("node [%08llx + %08llx]: inserted at\n%s",
               node->start, node->size, buf);
     }
 
     kfree(buf);
 }
 
 #undef STACKDEPTH
 #undef BUFSZ
 #else
 static void save_stack(struct drm_mm_node *node) { }
 static void show_leaks(struct drm_mm *mm) { }
 #endif
 
 #define START(node) ((node)->start)
 #define LAST(node)  ((node)->start + (node)->size - 1)
 
 INTERVAL_TREE_DEFINE(struct drm_mm_node, rb,
              u64, __subtree_last,
              START, LAST, static inline, drm_mm_interval_tree)
 
 struct drm_mm_node *
 __drm_mm_interval_first(const struct drm_mm *mm, u64 start, u64 last)
 {
     return drm_mm_interval_tree_iter_first((struct rb_root_cached *)&mm->interval_tree,
                            start, last) ?: (struct drm_mm_node *)&mm->head_node;
 }
 EXPORT_SYMBOL(__drm_mm_interval_first);
 
 static void drm_mm_interval_tree_add_node(struct drm_mm_node *hole_node,
                       struct drm_mm_node *node)
 {
     struct drm_mm *mm = hole_node->mm;
     struct rb_node **link, *rb;
     struct drm_mm_node *parent;
     bool leftmost;
 
     node->__subtree_last = LAST(node);
 
     if (drm_mm_node_allocated(hole_node)) {
         rb = &hole_node->rb;
         while (rb) {
             parent = rb_entry(rb, struct drm_mm_node, rb);
             if (parent->__subtree_last >= node->__subtree_last)
                 break;
 
             parent->__subtree_last = node->__subtree_last;
             rb = rb_parent(rb);
         }
 
         rb = &hole_node->rb;
         link = &hole_node->rb.rb_right;
         leftmost = false;
     } else {
         rb = NULL;
         link = &mm->interval_tree.rb_root.rb_node;
         leftmost = true;
     }
 
     while (*link) {
         rb = *link;
         parent = rb_entry(rb, struct drm_mm_node, rb);
         if (parent->__subtree_last < node->__subtree_last)
             parent->__subtree_last = node->__subtree_last;
         if (node->start < parent->start) {
             link = &parent->rb.rb_left;
         } else {
             link = &parent->rb.rb_right;
             leftmost = false;
         }
     }
 
     rb_link_node(&node->rb, rb, link);
     rb_insert_augmented_cached(&node->rb, &mm->interval_tree, leftmost,
                    &drm_mm_interval_tree_augment);
 }
 
 #define HOLE_SIZE(NODE) ((NODE)->hole_size)
 #define HOLE_ADDR(NODE) (__drm_mm_hole_node_start(NODE))
 
 static u64 rb_to_hole_size(struct rb_node *rb)
 {
     return rb_entry(rb, struct drm_mm_node, rb_hole_size)->hole_size;
 }
 
 static void insert_hole_size(struct rb_root_cached *root,
                  struct drm_mm_node *node)
 {
     struct rb_node **link = &root->rb_root.rb_node, *rb = NULL;
     u64 x = node->hole_size;
     bool first = true;
 
     while (*link) {
         rb = *link;
         if (x > rb_to_hole_size(rb)) {
             link = &rb->rb_left;
         } else {
             link = &rb->rb_right;
             first = false;
         }
     }
 
     rb_link_node(&node->rb_hole_size, rb, link);
     rb_insert_color_cached(&node->rb_hole_size, root, first);
 }
 
 RB_DECLARE_CALLBACKS_MAX(static, augment_callbacks,
              struct drm_mm_node, rb_hole_addr,
              u64, subtree_max_hole, HOLE_SIZE)
 
 static void insert_hole_addr(struct rb_root *root, struct drm_mm_node *node)
 {
     struct rb_node **link = &root->rb_node, *rb_parent = NULL;
     u64 start = HOLE_ADDR(node), subtree_max_hole = node->subtree_max_hole;
     struct drm_mm_node *parent;
 
     while (*link) {
         rb_parent = *link;
         parent = rb_entry(rb_parent, struct drm_mm_node, rb_hole_addr);
         if (parent->subtree_max_hole < subtree_max_hole)
             parent->subtree_max_hole = subtree_max_hole;
         if (start < HOLE_ADDR(parent))
             link = &parent->rb_hole_addr.rb_left;
         else
             link = &parent->rb_hole_addr.rb_right;
     }
 
     rb_link_node(&node->rb_hole_addr, rb_parent, link);
     rb_insert_augmented(&node->rb_hole_addr, root, &augment_callbacks);
 }
 
 static void add_hole(struct drm_mm_node *node)
 {
     struct drm_mm *mm = node->mm;
 
     node->hole_size =
         __drm_mm_hole_node_end(node) - __drm_mm_hole_node_start(node);
     node->subtree_max_hole = node->hole_size;
     DRM_MM_BUG_ON(!drm_mm_hole_follows(node));
 
     insert_hole_size(&mm->holes_size, node);
     insert_hole_addr(&mm->holes_addr, node);
 
     list_add(&node->hole_stack, &mm->hole_stack);
 }
 
 static void rm_hole(struct drm_mm_node *node)
 {
     DRM_MM_BUG_ON(!drm_mm_hole_follows(node));
 
     list_del(&node->hole_stack);
     rb_erase_cached(&node->rb_hole_size, &node->mm->holes_size);
     rb_erase_augmented(&node->rb_hole_addr, &node->mm->holes_addr,
                &augment_callbacks);
     node->hole_size = 0;
     node->subtree_max_hole = 0;
 
     DRM_MM_BUG_ON(drm_mm_hole_follows(node));
 }
 
 static inline struct drm_mm_node *rb_hole_size_to_node(struct rb_node *rb)
 {
     return rb_entry_safe(rb, struct drm_mm_node, rb_hole_size);
 }
 
 static inline struct drm_mm_node *rb_hole_addr_to_node(struct rb_node *rb)
 {
     return rb_entry_safe(rb, struct drm_mm_node, rb_hole_addr);
 }
 
 static struct drm_mm_node *best_hole(struct drm_mm *mm, u64 size)
 {
     struct rb_node *rb = mm->holes_size.rb_root.rb_node;
     struct drm_mm_node *best = NULL;
 
     do {
         struct drm_mm_node *node =
             rb_entry(rb, struct drm_mm_node, rb_hole_size);
 
         if (size <= node->hole_size) {
             best = node;
             rb = rb->rb_right;
         } else {
             rb = rb->rb_left;
         }
     } while (rb);
 
     return best;
 }
 
 static bool usable_hole_addr(struct rb_node *rb, u64 size)
 {
     return rb && rb_hole_addr_to_node(rb)->subtree_max_hole >= size;
 }
 
 static struct drm_mm_node *find_hole_addr(struct drm_mm *mm, u64 addr, u64 size)
 {
     struct rb_node *rb = mm->holes_addr.rb_node;
     struct drm_mm_node *node = NULL;
 
     while (rb) {
         u64 hole_start;
 
         if (!usable_hole_addr(rb, size))
             break;
 
         node = rb_hole_addr_to_node(rb);
         hole_start = __drm_mm_hole_node_start(node);
 
         if (addr < hole_start)
             rb = node->rb_hole_addr.rb_left;
         else if (addr > hole_start + node->hole_size)
             rb = node->rb_hole_addr.rb_right;
         else
             break;
     }
 
     return node;
 }
 
 static struct drm_mm_node *
 first_hole(struct drm_mm *mm,
        u64 start, u64 end, u64 size,
        enum drm_mm_insert_mode mode)
 {
     switch (mode) {
     default:
     case DRM_MM_INSERT_BEST:
         return best_hole(mm, size);
 
     case DRM_MM_INSERT_LOW:
         return find_hole_addr(mm, start, size);
 
     case DRM_MM_INSERT_HIGH:
         return find_hole_addr(mm, end, size);
 
     case DRM_MM_INSERT_EVICT:
         return list_first_entry_or_null(&mm->hole_stack,
                         struct drm_mm_node,
                         hole_stack);
     }
 }
 
 /**
  * DECLARE_NEXT_HOLE_ADDR - macro to declare next hole functions
  * @name: name of function to declare
  * @first: first rb member to traverse (either rb_left or rb_right).
  * @last: last rb member to traverse (either rb_right or rb_left).
  *
  * This macro declares a function to return the next hole of the addr rb tree.
  * While traversing the tree we take the searched size into account and only
  * visit branches with potential big enough holes.
  */
 
 #define DECLARE_NEXT_HOLE_ADDR(name, first, last)           \
 static struct drm_mm_node *name(struct drm_mm_node *entry, u64 size)    \
 {                                   \
     struct rb_node *parent, *node = &entry->rb_hole_addr;       \
                                     \
     if (!entry || RB_EMPTY_NODE(node))              \
         return NULL;                        \
                                     \
     if (usable_hole_addr(node->first, size)) {          \
         node = node->first;                 \
         while (usable_hole_addr(node->last, size))      \
             node = node->last;              \
         return rb_hole_addr_to_node(node);          \
     }                               \
                                     \
     while ((parent = rb_parent(node)) && node == parent->first) \
         node = parent;                      \
                                     \
     return rb_hole_addr_to_node(parent);                \
 }
 
 DECLARE_NEXT_HOLE_ADDR(next_hole_high_addr, rb_left, rb_right)
 DECLARE_NEXT_HOLE_ADDR(next_hole_low_addr, rb_right, rb_left)
 
 static struct drm_mm_node *
 next_hole(struct drm_mm *mm,
       struct drm_mm_node *node,
       u64 size,
       enum drm_mm_insert_mode mode)
 {
     switch (mode) {
     default:
     case DRM_MM_INSERT_BEST:
         return rb_hole_size_to_node(rb_prev(&node->rb_hole_size));
 
     case DRM_MM_INSERT_LOW:
         return next_hole_low_addr(node, size);
 
     case DRM_MM_INSERT_HIGH:
         return next_hole_high_addr(node, size);
 
     case DRM_MM_INSERT_EVICT:
         node = list_next_entry(node, hole_stack);
         return &node->hole_stack == &mm->hole_stack ? NULL : node;
     }
 }
 
 /**
  * drm_mm_reserve_node - insert an pre-initialized node
  * @mm: drm_mm allocator to insert @node into
  * @node: drm_mm_node to insert
  *
  * This functions inserts an already set-up &drm_mm_node into the allocator,
  * meaning that start, size and color must be set by the caller. All other
  * fields must be cleared to 0. This is useful to initialize the allocator with
  * preallocated objects which must be set-up before the range allocator can be
  * set-up, e.g. when taking over a firmware framebuffer.
  *
  * Returns:
  * 0 on success, -ENOSPC if there's no hole where @node is.
  */
 int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)
 {
     struct drm_mm_node *hole;
     u64 hole_start, hole_end;
     u64 adj_start, adj_end;
     u64 end;
 
     end = node->start + node->size;
     if (unlikely(end <= node->start))
         return -ENOSPC;
 
     /* Find the relevant hole to add our node to */
     hole = find_hole_addr(mm, node->start, 0);
     if (!hole)
         return -ENOSPC;
 
     adj_start = hole_start = __drm_mm_hole_node_start(hole);
     adj_end = hole_end = hole_start + hole->hole_size;
 
     if (mm->color_adjust)
         mm->color_adjust(hole, node->color, &adj_start, &adj_end);
 
     if (adj_start > node->start || adj_end < end)
         return -ENOSPC;
 
     node->mm = mm;
 
     __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
     list_add(&node->node_list, &hole->node_list);
     drm_mm_interval_tree_add_node(hole, node);
     node->hole_size = 0;
 
     rm_hole(hole);
     if (node->start > hole_start)
         add_hole(hole);
     if (end < hole_end)
         add_hole(node);
 
     save_stack(node);
     return 0;
 }
 EXPORT_SYMBOL(drm_mm_reserve_node);
 
 static u64 rb_to_hole_size_or_zero(struct rb_node *rb)
 {
     return rb ? rb_to_hole_size(rb) : 0;
 }
 
 /**
  * drm_mm_insert_node_in_range - ranged search for space and insert @node
  * @mm: drm_mm to allocate from
  * @node: preallocate node to insert
  * @size: size of the allocation
  * @alignment: alignment of the allocation
  * @color: opaque tag value to use for this node
  * @range_start: start of the allowed range for this node
  * @range_end: end of the allowed range for this node
  * @mode: fine-tune the allocation search and placement
  *
  * The preallocated @node must be cleared to 0.
  *
  * Returns:
  * 0 on success, -ENOSPC if there's no suitable hole.
  */
 int drm_mm_insert_node_in_range(struct drm_mm * const mm,
                 struct drm_mm_node * const node,
                 u64 size, u64 alignment,
                 unsigned long color,
                 u64 range_start, u64 range_end,
                 enum drm_mm_insert_mode mode)
 {
     struct drm_mm_node *hole;
     u64 remainder_mask;
     bool once;
 
     DRM_MM_BUG_ON(range_start > range_end);
 
     if (unlikely(size == 0 || range_end - range_start < size))
         return -ENOSPC;
 
     if (rb_to_hole_size_or_zero(rb_first_cached(&mm->holes_size)) < size)
         return -ENOSPC;
 
     if (alignment <= 1)
         alignment = 0;
 
     once = mode & DRM_MM_INSERT_ONCE;
     mode &= ~DRM_MM_INSERT_ONCE;
 
     remainder_mask = is_power_of_2(alignment) ? alignment - 1 : 0;
     for (hole = first_hole(mm, range_start, range_end, size, mode);
          hole;
          hole = once ? NULL : next_hole(mm, hole, size, mode)) {
         u64 hole_start = __drm_mm_hole_node_start(hole);
         u64 hole_end = hole_start + hole->hole_size;
         u64 adj_start, adj_end;
         u64 col_start, col_end;
 
         if (mode == DRM_MM_INSERT_LOW && hole_start >= range_end)
             break;
 
         if (mode == DRM_MM_INSERT_HIGH && hole_end <= range_start)
             break;
 
         col_start = hole_start;
         col_end = hole_end;
         if (mm->color_adjust)
             mm->color_adjust(hole, color, &col_start, &col_end);
 
         adj_start = max(col_start, range_start);
         adj_end = min(col_end, range_end);
 
         if (adj_end <= adj_start || adj_end - adj_start < size)
             continue;
 
         if (mode == DRM_MM_INSERT_HIGH)
             adj_start = adj_end - size;
 
         if (alignment) {
             u64 rem;
 
             if (likely(remainder_mask))
                 rem = adj_start & remainder_mask;
             else
                 div64_u64_rem(adj_start, alignment, &rem);
             if (rem) {
                 adj_start -= rem;
                 if (mode != DRM_MM_INSERT_HIGH)
                     adj_start += alignment;
 
                 if (adj_start < max(col_start, range_start) ||
                     min(col_end, range_end) - adj_start < size)
                     continue;
 
                 if (adj_end <= adj_start ||
                     adj_end - adj_start < size)
                     continue;
             }
         }
 
         node->mm = mm;
         node->size = size;
         node->start = adj_start;
         node->color = color;
         node->hole_size = 0;
 
         __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
         list_add(&node->node_list, &hole->node_list);
         drm_mm_interval_tree_add_node(hole, node);
 
         rm_hole(hole);
         if (adj_start > hole_start)
             add_hole(hole);
         if (adj_start + size < hole_end)
             add_hole(node);
 
         save_stack(node);
         return 0;
     }
 
     return -ENOSPC;
 }
 EXPORT_SYMBOL(drm_mm_insert_node_in_range);
 
 static inline bool drm_mm_node_scanned_block(const struct drm_mm_node *node)
 {
     return test_bit(DRM_MM_NODE_SCANNED_BIT, &node->flags);
 }
 
 /**
  * drm_mm_remove_node - Remove a memory node from the allocator.
  * @node: drm_mm_node to remove
  *
  * This just removes a node from its drm_mm allocator. The node does not need to
  * be cleared again before it can be re-inserted into this or any other drm_mm
  * allocator. It is a bug to call this function on a unallocated node.
  */
 void drm_mm_remove_node(struct drm_mm_node *node)
 {
     struct drm_mm *mm = node->mm;
     struct drm_mm_node *prev_node;
 
     DRM_MM_BUG_ON(!drm_mm_node_allocated(node));
     DRM_MM_BUG_ON(drm_mm_node_scanned_block(node));
 
     prev_node = list_prev_entry(node, node_list);
 
     if (drm_mm_hole_follows(node))
         rm_hole(node);
 
     drm_mm_interval_tree_remove(node, &mm->interval_tree);
     list_del(&node->node_list);
 
     if (drm_mm_hole_follows(prev_node))
         rm_hole(prev_node);
     add_hole(prev_node);
 
     clear_bit_unlock(DRM_MM_NODE_ALLOCATED_BIT, &node->flags);
 }
 EXPORT_SYMBOL(drm_mm_remove_node);
 
 /**
  * drm_mm_replace_node - move an allocation from @old to @new
  * @old: drm_mm_node to remove from the allocator
  * @new: drm_mm_node which should inherit @old's allocation
  *
  * This is useful for when drivers embed the drm_mm_node structure and hence
  * can't move allocations by reassigning pointers. It's a combination of remove
  * and insert with the guarantee that the allocation start will match.
  */
 void drm_mm_replace_node(struct drm_mm_node *old, struct drm_mm_node *new)
 {
     struct drm_mm *mm = old->mm;
 
     DRM_MM_BUG_ON(!drm_mm_node_allocated(old));
 
     *new = *old;
 
     __set_bit(DRM_MM_NODE_ALLOCATED_BIT, &new->flags);
     list_replace(&old->node_list, &new->node_list);
     rb_replace_node_cached(&old->rb, &new->rb, &mm->interval_tree);
 
     if (drm_mm_hole_follows(old)) {
         list_replace(&old->hole_stack, &new->hole_stack);
         rb_replace_node_cached(&old->rb_hole_size,
                        &new->rb_hole_size,
                        &mm->holes_size);
         rb_replace_node(&old->rb_hole_addr,
                 &new->rb_hole_addr,
                 &mm->holes_addr);
     }
 
     clear_bit_unlock(DRM_MM_NODE_ALLOCATED_BIT, &old->flags);
 }
 EXPORT_SYMBOL(drm_mm_replace_node);
 
 /**
  * DOC: lru scan roster
  *
  * Very often GPUs need to have continuous allocations for a given object. When
  * evicting objects to make space for a new one it is therefore not most
  * efficient when we simply start to select all objects from the tail of an LRU
  * until there's a suitable hole: Especially for big objects or nodes that
  * otherwise have special allocation constraints there's a good chance we evict
  * lots of (smaller) objects unnecessarily.
  *
  * The DRM range allocator supports this use-case through the scanning
  * interfaces. First a scan operation needs to be initialized with
  * drm_mm_scan_init() or drm_mm_scan_init_with_range(). The driver adds
  * objects to the roster, probably by walking an LRU list, but this can be
  * freely implemented. Eviction candidates are added using
  * drm_mm_scan_add_block() until a suitable hole is found or there are no
  * further evictable objects. Eviction roster metadata is tracked in &struct
  * drm_mm_scan.
  *
  * The driver must walk through all objects again in exactly the reverse
  * order to restore the allocator state. Note that while the allocator is used
  * in the scan mode no other operation is allowed.
  *
  * Finally the driver evicts all objects selected (drm_mm_scan_remove_block()
  * reported true) in the scan, and any overlapping nodes after color adjustment
  * (drm_mm_scan_color_evict()). Adding and removing an object is O(1), and
  * since freeing a node is also O(1) the overall complexity is
  * O(scanned_objects). So like the free stack which needs to be walked before a
  * scan operation even begins this is linear in the number of objects. It
  * doesn't seem to hurt too badly.
  */
 
 /**
  * drm_mm_scan_init_with_range - initialize range-restricted lru scanning
  * @scan: scan state
  * @mm: drm_mm to scan
  * @size: size of the allocation
  * @alignment: alignment of the allocation
  * @color: opaque tag value to use for the allocation
  * @start: start of the allowed range for the allocation
  * @end: end of the allowed range for the allocation
  * @mode: fine-tune the allocation search and placement
  *
  * This simply sets up the scanning routines with the parameters for the desired
  * hole.
  *
  * Warning:
  * As long as the scan list is non-empty, no other operations than
  * adding/removing nodes to/from the scan list are allowed.
  */
 void drm_mm_scan_init_with_range(struct drm_mm_scan *scan,
                  struct drm_mm *mm,
                  u64 size,
                  u64 alignment,
                  unsigned long color,
                  u64 start,
                  u64 end,
                  enum drm_mm_insert_mode mode)
 {
     DRM_MM_BUG_ON(start >= end);
     DRM_MM_BUG_ON(!size || size > end - start);
     DRM_MM_BUG_ON(mm->scan_active);
 
     scan->mm = mm;
 
     if (alignment <= 1)
         alignment = 0;
 
     scan->color = color;
     scan->alignment = alignment;
     scan->remainder_mask = is_power_of_2(alignment) ? alignment - 1 : 0;
     scan->size = size;
     scan->mode = mode;
 
     DRM_MM_BUG_ON(end <= start);
     scan->range_start = start;
     scan->range_end = end;
 
     scan->hit_start = U64_MAX;
     scan->hit_end = 0;
 }
 EXPORT_SYMBOL(drm_mm_scan_init_with_range);
 
 /**
  * drm_mm_scan_add_block - add a node to the scan list
  * @scan: the active drm_mm scanner
  * @node: drm_mm_node to add
  *
  * Add a node to the scan list that might be freed to make space for the desired
  * hole.
  *
  * Returns:
  * True if a hole has been found, false otherwise.
  */
 bool drm_mm_scan_add_block(struct drm_mm_scan *scan,
                struct drm_mm_node *node)
 {
     struct drm_mm *mm = scan->mm;
     struct drm_mm_node *hole;
     u64 hole_start, hole_end;
     u64 col_start, col_end;
     u64 adj_start, adj_end;
 
     DRM_MM_BUG_ON(node->mm != mm);
     DRM_MM_BUG_ON(!drm_mm_node_allocated(node));
     DRM_MM_BUG_ON(drm_mm_node_scanned_block(node));
     __set_bit(DRM_MM_NODE_SCANNED_BIT, &node->flags);
     mm->scan_active++;
 
     /* Remove this block from the node_list so that we enlarge the hole
      * (distance between the end of our previous node and the start of
      * or next), without poisoning the link so that we can restore it
      * later in drm_mm_scan_remove_block().
      */
     hole = list_prev_entry(node, node_list);
     DRM_MM_BUG_ON(list_next_entry(hole, node_list) != node);
     __list_del_entry(&node->node_list);
 
     hole_start = __drm_mm_hole_node_start(hole);
     hole_end = __drm_mm_hole_node_end(hole);
 
     col_start = hole_start;
     col_end = hole_end;
     if (mm->color_adjust)
         mm->color_adjust(hole, scan->color, &col_start, &col_end);
 
     adj_start = max(col_start, scan->range_start);
     adj_end = min(col_end, scan->range_end);
     if (adj_end <= adj_start || adj_end - adj_start < scan->size)
         return false;
 
     if (scan->mode == DRM_MM_INSERT_HIGH)
         adj_start = adj_end - scan->size;
 
     if (scan->alignment) {
         u64 rem;
 
         if (likely(scan->remainder_mask))
             rem = adj_start & scan->remainder_mask;
         else
             div64_u64_rem(adj_start, scan->alignment, &rem);
         if (rem) {
             adj_start -= rem;
             if (scan->mode != DRM_MM_INSERT_HIGH)
                 adj_start += scan->alignment;
             if (adj_start < max(col_start, scan->range_start) ||
                 min(col_end, scan->range_end) - adj_start < scan->size)
                 return false;
 
             if (adj_end <= adj_start ||
                 adj_end - adj_start < scan->size)
                 return false;
         }
     }
 
     scan->hit_start = adj_start;
     scan->hit_end = adj_start + scan->size;
 
     DRM_MM_BUG_ON(scan->hit_start >= scan->hit_end);
     DRM_MM_BUG_ON(scan->hit_start < hole_start);
     DRM_MM_BUG_ON(scan->hit_end > hole_end);
 
     return true;
 }
 EXPORT_SYMBOL(drm_mm_scan_add_block);
 
 /**
  * drm_mm_scan_remove_block - remove a node from the scan list
  * @scan: the active drm_mm scanner
  * @node: drm_mm_node to remove
  *
  * Nodes **must** be removed in exactly the reverse order from the scan list as
  * they have been added (e.g. using list_add() as they are added and then
  * list_for_each() over that eviction list to remove), otherwise the internal
  * state of the memory manager will be corrupted.
  *
  * When the scan list is empty, the selected memory nodes can be freed. An
  * immediately following drm_mm_insert_node_in_range_generic() or one of the
  * simpler versions of that function with !DRM_MM_SEARCH_BEST will then return
  * the just freed block (because it's at the top of the free_stack list).
  *
  * Returns:
  * True if this block should be evicted, false otherwise. Will always
  * return false when no hole has been found.
  */
 bool drm_mm_scan_remove_block(struct drm_mm_scan *scan,
                   struct drm_mm_node *node)
 {
     struct drm_mm_node *prev_node;
 
     DRM_MM_BUG_ON(node->mm != scan->mm);
     DRM_MM_BUG_ON(!drm_mm_node_scanned_block(node));
     __clear_bit(DRM_MM_NODE_SCANNED_BIT, &node->flags);
 
     DRM_MM_BUG_ON(!node->mm->scan_active);
     node->mm->scan_active--;
 
     /* During drm_mm_scan_add_block() we decoupled this node leaving
      * its pointers intact. Now that the caller is walking back along
      * the eviction list we can restore this block into its rightful
      * place on the full node_list. To confirm that the caller is walking
      * backwards correctly we check that prev_node->next == node->next,
      * i.e. both believe the same node should be on the other side of the
      * hole.
      */
     prev_node = list_prev_entry(node, node_list);
     DRM_MM_BUG_ON(list_next_entry(prev_node, node_list) !=
               list_next_entry(node, node_list));
     list_add(&node->node_list, &prev_node->node_list);
 
     return (node->start + node->size > scan->hit_start &&
         node->start < scan->hit_end);
 }
 EXPORT_SYMBOL(drm_mm_scan_remove_block);
 
 /**
  * drm_mm_scan_color_evict - evict overlapping nodes on either side of hole
  * @scan: drm_mm scan with target hole
  *
  * After completing an eviction scan and removing the selected nodes, we may
  * need to remove a few more nodes from either side of the target hole if
  * mm.color_adjust is being used.
  *
  * Returns:
  * A node to evict, or NULL if there are no overlapping nodes.
  */
 struct drm_mm_node *drm_mm_scan_color_evict(struct drm_mm_scan *scan)
 {
     struct drm_mm *mm = scan->mm;
     struct drm_mm_node *hole;
     u64 hole_start, hole_end;
 
     DRM_MM_BUG_ON(list_empty(&mm->hole_stack));
 
     if (!mm->color_adjust)
         return NULL;
 
     /*
      * The hole found during scanning should ideally be the first element
      * in the hole_stack list, but due to side-effects in the driver it
      * may not be.
      */
     list_for_each_entry(hole, &mm->hole_stack, hole_stack) {
         hole_start = __drm_mm_hole_node_start(hole);
         hole_end = hole_start + hole->hole_size;
 
         if (hole_start <= scan->hit_start &&
             hole_end >= scan->hit_end)
             break;
     }
 
     /* We should only be called after we found the hole previously */
     DRM_MM_BUG_ON(&hole->hole_stack == &mm->hole_stack);
     if (unlikely(&hole->hole_stack == &mm->hole_stack))
         return NULL;
 
     DRM_MM_BUG_ON(hole_start > scan->hit_start);
     DRM_MM_BUG_ON(hole_end < scan->hit_end);
 
     mm->color_adjust(hole, scan->color, &hole_start, &hole_end);
     if (hole_start > scan->hit_start)
         return hole;
     if (hole_end < scan->hit_end)
         return list_next_entry(hole, node_list);
 
     return NULL;
 }
 EXPORT_SYMBOL(drm_mm_scan_color_evict);
 
 /**
  * drm_mm_init - initialize a drm-mm allocator
  * @mm: the drm_mm structure to initialize
  * @start: start of the range managed by @mm
  * @size: end of the range managed by @mm
  *
  * Note that @mm must be cleared to 0 before calling this function.
  */
 void drm_mm_init(struct drm_mm *mm, u64 start, u64 size)
 {
     DRM_MM_BUG_ON(start + size <= start);
 
     mm->color_adjust = NULL;
 
     INIT_LIST_HEAD(&mm->hole_stack);
     mm->interval_tree = RB_ROOT_CACHED;
     mm->holes_size = RB_ROOT_CACHED;
     mm->holes_addr = RB_ROOT;
 
     /* Clever trick to avoid a special case in the free hole tracking. */
     INIT_LIST_HEAD(&mm->head_node.node_list);
     mm->head_node.flags = 0;
     mm->head_node.mm = mm;
     mm->head_node.start = start + size;
     mm->head_node.size = -size;
     add_hole(&mm->head_node);
 
     mm->scan_active = 0;
 
 #ifdef CONFIG_DRM_DEBUG_MM
     stack_depot_init();
 #endif
 }
 EXPORT_SYMBOL(drm_mm_init);
 
 /**
  * drm_mm_takedown - clean up a drm_mm allocator
  * @mm: drm_mm allocator to clean up
  *
  * Note that it is a bug to call this function on an allocator which is not
  * clean.
  */
 void drm_mm_takedown(struct drm_mm *mm)
 {
     if (WARN(!drm_mm_clean(mm),
          "Memory manager not clean during takedown.\n"))
         show_leaks(mm);
 }
 EXPORT_SYMBOL(drm_mm_takedown);
 
 static u64 drm_mm_dump_hole(struct drm_printer *p, const struct drm_mm_node *entry)
 {
     u64 start, size;
 
     size = entry->hole_size;
     if (size) {
         start = drm_mm_hole_node_start(entry);
         drm_printf(p, "%#018llx-%#018llx: %llu: free\n",
                start, start + size, size);
     }
 
     return size;
 }
 /**
  * drm_mm_print - print allocator state
  * @mm: drm_mm allocator to print
  * @p: DRM printer to use
  */
 void drm_mm_print(const struct drm_mm *mm, struct drm_printer *p)
 {
     const struct drm_mm_node *entry;
     u64 total_used = 0, total_free = 0, total = 0;
 
     total_free += drm_mm_dump_hole(p, &mm->head_node);
 
     drm_mm_for_each_node(entry, mm) {
         drm_printf(p, "%#018llx-%#018llx: %llu: used\n", entry->start,
                entry->start + entry->size, entry->size);
         total_used += entry->size;
         total_free += drm_mm_dump_hole(p, entry);
     }
     total = total_free + total_used;
 
     drm_printf(p, "total: %llu, used %llu free %llu\n", total,
            total_used, total_free);
 }
 EXPORT_SYMBOL(drm_mm_print);

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