drm: mm: track free areas implicitly

The idea is to track free holes implicitly by marking the allocation
immediatly preceeding a hole.

To avoid an ugly corner case add a dummy head_node to struct drm_mm
to track the hole that spans to complete allocation area when the
memory manager is empty.

To guarantee that there's always a preceeding/following node (that might
be marked as hole_follows == 1), move the mm->node_list list_head to the
head_node.

The main allocator and fair-lru scan code actually becomes simpler.
Only the debug code slightly suffers because free areas are no longer
explicit.

Also add drm_mm_for_each_node (which will be much more useful when
struct drm_mm_node is embeddable).

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

2 files changed, 225 insertions, 260 deletions

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index c59515ba7e69..4fa33e1283af 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -64,8 +64,8 @@ static struct drm_mm_node *drm_mm_kmalloc(struct drm_mm *mm, int atomic)
                 else {
                         child =
                             list_entry(mm->unused_nodes.next,
-                                       struct drm_mm_node, free_stack);
-                        list_del(&child->free_stack);
+                                       struct drm_mm_node, node_list);
+                        list_del(&child->node_list);
                         --mm->num_unused;
                 }
                 spin_unlock(&mm->unused_lock);
@@ -94,126 +94,123 @@ int drm_mm_pre_get(struct drm_mm *mm)
                         return ret;
                 }
                 ++mm->num_unused;
-                list_add_tail(&node->free_stack, &mm->unused_nodes);
+                list_add_tail(&node->node_list, &mm->unused_nodes);
         }
         spin_unlock(&mm->unused_lock);
         return 0;
 }
 EXPORT_SYMBOL(drm_mm_pre_get);
 
-static int drm_mm_create_tail_node(struct drm_mm *mm,
-                                   unsigned long start,
-                                   unsigned long size, int atomic)
+static inline unsigned long drm_mm_hole_node_start(struct drm_mm_node *hole_node)
 {
-        struct drm_mm_node *child;
-
-        child = drm_mm_kmalloc(mm, atomic);
-        if (unlikely(child == NULL))
-                return -ENOMEM;
-
-        child->free = 1;
-        child->size = size;
-        child->start = start;
-        child->mm = mm;
-
-        list_add_tail(&child->node_list, &mm->node_list);
-        list_add_tail(&child->free_stack, &mm->free_stack);
-
-        return 0;
+        return hole_node->start + hole_node->size;
 }
 
-static struct drm_mm_node *drm_mm_split_at_start(struct drm_mm_node *parent,
-                                                 unsigned long size,
-                                                 int atomic)
+static inline unsigned long drm_mm_hole_node_end(struct drm_mm_node *hole_node)
 {
-        struct drm_mm_node *child;
-
-        child = drm_mm_kmalloc(parent->mm, atomic);
-        if (unlikely(child == NULL))
-                return NULL;
-
-        INIT_LIST_HEAD(&child->free_stack);
+        struct drm_mm_node *next_node =
+                list_entry(hole_node->node_list.next, struct drm_mm_node,
+                           node_list);
 
-        child->size = size;
-        child->start = parent->start;
-        child->mm = parent->mm;
-
-        list_add_tail(&child->node_list, &parent->node_list);
-        INIT_LIST_HEAD(&child->free_stack);
-
-        parent->size -= size;
-        parent->start += size;
-        return child;
+        return next_node->start;
 }
 
-
-struct drm_mm_node *drm_mm_get_block_generic(struct drm_mm_node *node,
+struct drm_mm_node *drm_mm_get_block_generic(struct drm_mm_node *hole_node,
                                              unsigned long size,
                                              unsigned alignment,
                                              int atomic)
 {
 
-        struct drm_mm_node *align_splitoff = NULL;
-        unsigned tmp = 0;
+        struct drm_mm_node *node;
+        struct drm_mm *mm = hole_node->mm;
+        unsigned long tmp = 0, wasted = 0;
+        unsigned long hole_start = drm_mm_hole_node_start(hole_node);
+        unsigned long hole_end = drm_mm_hole_node_end(hole_node);
+
+        BUG_ON(!hole_node->hole_follows);
+
+        node = drm_mm_kmalloc(mm, atomic);
+        if (unlikely(node == NULL))
+                return NULL;
 
         if (alignment)
-                tmp = node->start % alignment;
+                tmp = hole_start % alignment;
 
-        if (tmp) {
-                align_splitoff =
-                    drm_mm_split_at_start(node, alignment - tmp, atomic);
-                if (unlikely(align_splitoff == NULL))
-                        return NULL;
-        }
+        if (!tmp) {
+                hole_node->hole_follows = 0;
+                list_del_init(&hole_node->hole_stack);
+        } else
+                wasted = alignment - tmp;
+
+        node->start = hole_start + wasted;
+        node->size = size;
+        node->mm = mm;
 
-        if (node->size == size) {
-                list_del_init(&node->free_stack);
-                node->free = 0;
+        INIT_LIST_HEAD(&node->hole_stack);
+        list_add(&node->node_list, &hole_node->node_list);
+
+        BUG_ON(node->start + node->size > hole_end);
+
+        if (node->start + node->size < hole_end) {
+                list_add(&node->hole_stack, &mm->hole_stack);
+                node->hole_follows = 1;
         } else {
-                node = drm_mm_split_at_start(node, size, atomic);
+                node->hole_follows = 0;
         }
 
-        if (align_splitoff)
-                drm_mm_put_block(align_splitoff);
-
         return node;
 }
 EXPORT_SYMBOL(drm_mm_get_block_generic);
 
-struct drm_mm_node *drm_mm_get_block_range_generic(struct drm_mm_node *node,
+struct drm_mm_node *drm_mm_get_block_range_generic(struct drm_mm_node *hole_node,
                                                 unsigned long size,
                                                 unsigned alignment,
                                                 unsigned long start,
                                                 unsigned long end,
                                                 int atomic)
 {
-        struct drm_mm_node *align_splitoff = NULL;
-        unsigned tmp = 0;
-        unsigned wasted = 0;
+        struct drm_mm_node *node;
+        struct drm_mm *mm = hole_node->mm;
+        unsigned long tmp = 0, wasted = 0;
+        unsigned long hole_start = drm_mm_hole_node_start(hole_node);
+        unsigned long hole_end = drm_mm_hole_node_end(hole_node);
 
-        if (node->start < start)
-                wasted += start - node->start;
+        BUG_ON(!hole_node->hole_follows);
+
+        node = drm_mm_kmalloc(mm, atomic);
+        if (unlikely(node == NULL))
+                return NULL;
+
+        if (hole_start < start)
+                wasted += start - hole_start;
         if (alignment)
-                tmp = ((node->start + wasted) % alignment);
+                tmp = (hole_start + wasted) % alignment;
 
         if (tmp)
                 wasted += alignment - tmp;
-        if (wasted) {
-                align_splitoff = drm_mm_split_at_start(node, wasted, atomic);
-                if (unlikely(align_splitoff == NULL))
-                        return NULL;
+
+        if (!wasted) {
+                hole_node->hole_follows = 0;
+                list_del_init(&hole_node->hole_stack);
         }
 
-        if (node->size == size) {
-                list_del_init(&node->free_stack);
-                node->free = 0;
+        node->start = hole_start + wasted;
+        node->size = size;
+        node->mm = mm;
+
+        INIT_LIST_HEAD(&node->hole_stack);
+        list_add(&node->node_list, &hole_node->node_list);
+
+        BUG_ON(node->start + node->size > hole_end);
+        BUG_ON(node->start + node->size > end);
+
+        if (node->start + node->size < hole_end) {
+                list_add(&node->hole_stack, &mm->hole_stack);
+                node->hole_follows = 1;
         } else {
-                node = drm_mm_split_at_start(node, size, atomic);
+                node->hole_follows = 0;
         }
 
-        if (align_splitoff)
-                drm_mm_put_block(align_splitoff);
-
         return node;
 }
 EXPORT_SYMBOL(drm_mm_get_block_range_generic);
@@ -223,66 +220,41 @@ EXPORT_SYMBOL(drm_mm_get_block_range_generic);
  * Otherwise add to the free stack.
  */
 
-void drm_mm_put_block(struct drm_mm_node *cur)
+void drm_mm_put_block(struct drm_mm_node *node)
 {
 
-        struct drm_mm *mm = cur->mm;
-        struct list_head *cur_head = &cur->node_list;
-        struct list_head *root_head = &mm->node_list;
-        struct drm_mm_node *prev_node = NULL;
-        struct drm_mm_node *next_node;
+        struct drm_mm *mm = node->mm;
+        struct drm_mm_node *prev_node;
 
-        int merged = 0;
+        BUG_ON(node->scanned_block || node->scanned_prev_free
+                                   || node->scanned_next_free);
 
-        BUG_ON(cur->scanned_block || cur->scanned_prev_free
-                                  || cur->scanned_next_free);
+        prev_node =
+            list_entry(node->node_list.prev, struct drm_mm_node, node_list);
 
-        if (cur_head->prev != root_head) {
-                prev_node =
-                    list_entry(cur_head->prev, struct drm_mm_node, node_list);
-                if (prev_node->free) {
-                        prev_node->size += cur->size;
-                        merged = 1;
-                }
-        }
-        if (cur_head->next != root_head) {
-                next_node =
-                    list_entry(cur_head->next, struct drm_mm_node, node_list);
-                if (next_node->free) {
-                        if (merged) {
-                                prev_node->size += next_node->size;
-                                list_del(&next_node->node_list);
-                                list_del(&next_node->free_stack);
-                                spin_lock(&mm->unused_lock);
-                                if (mm->num_unused < MM_UNUSED_TARGET) {
-                                        list_add(&next_node->free_stack,
-                                                 &mm->unused_nodes);
-                                        ++mm->num_unused;
-                                } else
-                                        kfree(next_node);
-                                spin_unlock(&mm->unused_lock);
-                        } else {
-                                next_node->size += cur->size;
-                                next_node->start = cur->start;
-                                merged = 1;
-                        }
-                }
-        }
-        if (!merged) {
-                cur->free = 1;
-                list_add(&cur->free_stack, &mm->free_stack);
-        } else {
-                list_del(&cur->node_list);
-                spin_lock(&mm->unused_lock);
-                if (mm->num_unused < MM_UNUSED_TARGET) {
-                        list_add(&cur->free_stack, &mm->unused_nodes);
-                        ++mm->num_unused;
-                } else
-                        kfree(cur);
-                spin_unlock(&mm->unused_lock);
-        }
-}
+        if (node->hole_follows) {
+                BUG_ON(drm_mm_hole_node_start(node)
+                                == drm_mm_hole_node_end(node));
+                list_del(&node->hole_stack);
+        } else
+                BUG_ON(drm_mm_hole_node_start(node)
+                                != drm_mm_hole_node_end(node));
 
+        if (!prev_node->hole_follows) {
+                prev_node->hole_follows = 1;
+                list_add(&prev_node->hole_stack, &mm->hole_stack);
+        } else
+                list_move(&prev_node->hole_stack, &mm->hole_stack);
+
+        list_del(&node->node_list);
+        spin_lock(&mm->unused_lock);
+        if (mm->num_unused < MM_UNUSED_TARGET) {
+                list_add(&node->node_list, &mm->unused_nodes);
+                ++mm->num_unused;
+        } else
+                kfree(node);
+        spin_unlock(&mm->unused_lock);
+}
 EXPORT_SYMBOL(drm_mm_put_block);
 
 static int check_free_hole(unsigned long start, unsigned long end,
@@ -319,8 +291,10 @@ struct drm_mm_node *drm_mm_search_free(const struct drm_mm *mm,
         best = NULL;
         best_size = ~0UL;
 
-        list_for_each_entry(entry, &mm->free_stack, free_stack) {
-                if (!check_free_hole(entry->start, entry->start + entry->size,
+        list_for_each_entry(entry, &mm->hole_stack, hole_stack) {
+                BUG_ON(!entry->hole_follows);
+                if (!check_free_hole(drm_mm_hole_node_start(entry),
+                                     drm_mm_hole_node_end(entry),
                                      size, alignment))
                         continue;
 
@@ -353,12 +327,13 @@ struct drm_mm_node *drm_mm_search_free_in_range(const struct drm_mm *mm,
         best = NULL;
         best_size = ~0UL;
 
-        list_for_each_entry(entry, &mm->free_stack, free_stack) {
-                unsigned long adj_start = entry->start < start ?
-                        start : entry->start;
-                unsigned long adj_end = entry->start + entry->size > end ?
-                        end : entry->start + entry->size;
+        list_for_each_entry(entry, &mm->hole_stack, hole_stack) {
+                unsigned long adj_start = drm_mm_hole_node_start(entry) < start ?
+                        start : drm_mm_hole_node_start(entry);
+                unsigned long adj_end = drm_mm_hole_node_end(entry) > end ?
+                        end : drm_mm_hole_node_end(entry);
 
+                BUG_ON(!entry->hole_follows);
                 if (!check_free_hole(adj_start, adj_end, size, alignment))
                         continue;
 
@@ -430,70 +405,40 @@ EXPORT_SYMBOL(drm_mm_init_scan_with_range);
 int drm_mm_scan_add_block(struct drm_mm_node *node)
 {
         struct drm_mm *mm = node->mm;
-        struct list_head *prev_free, *next_free;
-        struct drm_mm_node *prev_node, *next_node;
+        struct drm_mm_node *prev_node;
+        unsigned long hole_start, hole_end;
         unsigned long adj_start;
         unsigned long adj_end;
 
         mm->scanned_blocks++;
 
-        prev_free = next_free = NULL;
-
-        BUG_ON(node->free);
+        BUG_ON(node->scanned_block);
         node->scanned_block = 1;
-        node->free = 1;
-
-        if (node->node_list.prev != &mm->node_list) {
-                prev_node = list_entry(node->node_list.prev, struct drm_mm_node,
-                                       node_list);
-
-                if (prev_node->free) {
-                        list_del(&prev_node->node_list);
-
-                        node->start = prev_node->start;
-                        node->size += prev_node->size;
-
-                        prev_node->scanned_prev_free = 1;
-
-                        prev_free = &prev_node->free_stack;
-                }
-        }
-
-        if (node->node_list.next != &mm->node_list) {
-                next_node = list_entry(node->node_list.next, struct drm_mm_node,
-                                       node_list);
-
-                if (next_node->free) {
-                        list_del(&next_node->node_list);
-
-                        node->size += next_node->size;
-
-                        next_node->scanned_next_free = 1;
 
-                        next_free = &next_node->free_stack;
-                }
-        }
+        prev_node = list_entry(node->node_list.prev, struct drm_mm_node,
+                               node_list);
 
-        /* The free_stack list is not used for allocated objects, so these two
-         * pointers can be abused (as long as no allocations in this memory
-         * manager happens). */
-        node->free_stack.prev = prev_free;
-        node->free_stack.next = next_free;
+        node->scanned_preceeds_hole = prev_node->hole_follows;
+        prev_node->hole_follows = 1;
+        list_del(&node->node_list);
+        node->node_list.prev = &prev_node->node_list;
 
+        hole_start = drm_mm_hole_node_start(prev_node);
+        hole_end = drm_mm_hole_node_end(prev_node);
         if (mm->scan_check_range) {
-                adj_start = node->start < mm->scan_start ?
-                        mm->scan_start : node->start;
-                adj_end = node->start + node->size > mm->scan_end ?
-                        mm->scan_end : node->start + node->size;
+                adj_start = hole_start < mm->scan_start ?
+                        mm->scan_start : hole_start;
+                adj_end = hole_end > mm->scan_end ?
+                        mm->scan_end : hole_end;
         } else {
-                adj_start = node->start;
-                adj_end = node->start + node->size;
+                adj_start = hole_start;
+                adj_end = hole_end;
         }
 
         if (check_free_hole(adj_start , adj_end,
                             mm->scan_size, mm->scan_alignment)) {
-                mm->scan_hit_start = node->start;
-                mm->scan_hit_size = node->size;
+                mm->scan_hit_start = hole_start;
+                mm->scan_hit_size = hole_end;
 
                 return 1;
         }
@@ -519,39 +464,19 @@ EXPORT_SYMBOL(drm_mm_scan_add_block);
 int drm_mm_scan_remove_block(struct drm_mm_node *node)
 {
         struct drm_mm *mm = node->mm;
-        struct drm_mm_node *prev_node, *next_node;
+        struct drm_mm_node *prev_node;
 
         mm->scanned_blocks--;
 
         BUG_ON(!node->scanned_block);
         node->scanned_block = 0;
-        node->free = 0;
-
-        prev_node = list_entry(node->free_stack.prev, struct drm_mm_node,
-                               free_stack);
-        next_node = list_entry(node->free_stack.next, struct drm_mm_node,
-                               free_stack);
-
-        if (prev_node) {
-                BUG_ON(!prev_node->scanned_prev_free);
-                prev_node->scanned_prev_free = 0;
-
-                list_add_tail(&prev_node->node_list, &node->node_list);
 
-                node->start = prev_node->start + prev_node->size;
-                node->size -= prev_node->size;
-        }
-
-        if (next_node) {
-                BUG_ON(!next_node->scanned_next_free);
-                next_node->scanned_next_free = 0;
-
-                list_add(&next_node->node_list, &node->node_list);
-
-                node->size -= next_node->size;
-        }
+        prev_node = list_entry(node->node_list.prev, struct drm_mm_node,
+                               node_list);
 
-        INIT_LIST_HEAD(&node->free_stack);
+        prev_node->hole_follows = node->scanned_preceeds_hole;
+        INIT_LIST_HEAD(&node->node_list);
+        list_add(&node->node_list, &prev_node->node_list);
 
         /* Only need to check for containement because start&size for the
          * complete resulting free block (not just the desired part) is
@@ -568,7 +493,7 @@ EXPORT_SYMBOL(drm_mm_scan_remove_block);
 
 int drm_mm_clean(struct drm_mm * mm)
 {
-        struct list_head *head = &mm->node_list;
+        struct list_head *head = &mm->head_node.node_list;
 
         return (head->next->next == head);
 }
@@ -576,38 +501,40 @@ EXPORT_SYMBOL(drm_mm_clean);
 
 int drm_mm_init(struct drm_mm * mm, unsigned long start, unsigned long size)
 {
-        INIT_LIST_HEAD(&mm->node_list);
-        INIT_LIST_HEAD(&mm->free_stack);
+        INIT_LIST_HEAD(&mm->hole_stack);
         INIT_LIST_HEAD(&mm->unused_nodes);
         mm->num_unused = 0;
         mm->scanned_blocks = 0;
         spin_lock_init(&mm->unused_lock);
 
-        return drm_mm_create_tail_node(mm, start, size, 0);
+        /* Clever trick to avoid a special case in the free hole tracking. */
+        INIT_LIST_HEAD(&mm->head_node.node_list);
+        INIT_LIST_HEAD(&mm->head_node.hole_stack);
+        mm->head_node.hole_follows = 1;
+        mm->head_node.scanned_block = 0;
+        mm->head_node.scanned_prev_free = 0;
+        mm->head_node.scanned_next_free = 0;
+        mm->head_node.mm = mm;
+        mm->head_node.start = start + size;
+        mm->head_node.size = start - mm->head_node.start;
+        list_add_tail(&mm->head_node.hole_stack, &mm->hole_stack);
+
+        return 0;
 }
 EXPORT_SYMBOL(drm_mm_init);
 
 void drm_mm_takedown(struct drm_mm * mm)
 {
-        struct list_head *bnode = mm->free_stack.next;
-        struct drm_mm_node *entry;
-        struct drm_mm_node *next;
+        struct drm_mm_node *entry, *next;
 
-        entry = list_entry(bnode, struct drm_mm_node, free_stack);
-
-        if (entry->node_list.next != &mm->node_list ||
-            entry->free_stack.next != &mm->free_stack) {
+        if (!list_empty(&mm->head_node.node_list)) {
                 DRM_ERROR("Memory manager not clean. Delaying takedown\n");
                 return;
         }
 
-        list_del(&entry->free_stack);
-        list_del(&entry->node_list);
-        kfree(entry);
-
         spin_lock(&mm->unused_lock);
-        list_for_each_entry_safe(entry, next, &mm->unused_nodes, free_stack) {
-                list_del(&entry->free_stack);
+        list_for_each_entry_safe(entry, next, &mm->unused_nodes, node_list) {
+                list_del(&entry->node_list);
                 kfree(entry);
                 --mm->num_unused;
         }
@@ -620,19 +547,37 @@ EXPORT_SYMBOL(drm_mm_takedown);
 void drm_mm_debug_table(struct drm_mm *mm, const char *prefix)
 {
         struct drm_mm_node *entry;
-        int total_used = 0, total_free = 0, total = 0;
-
-        list_for_each_entry(entry, &mm->node_list, node_list) {
-                printk(KERN_DEBUG "%s 0x%08lx-0x%08lx: %8ld: %s\n",
+        unsigned long total_used = 0, total_free = 0, total = 0;
+        unsigned long hole_start, hole_end, hole_size;
+
+        hole_start = drm_mm_hole_node_start(&mm->head_node);
+        hole_end = drm_mm_hole_node_end(&mm->head_node);
+        hole_size = hole_end - hole_start;
+        if (hole_size)
+                printk(KERN_DEBUG "%s 0x%08lx-0x%08lx: %8lu: free\n",
+                        prefix, hole_start, hole_end,
+                        hole_size);
+        total_free += hole_size;
+
+        drm_mm_for_each_node(entry, mm) {
+                printk(KERN_DEBUG "%s 0x%08lx-0x%08lx: %8lu: used\n",
                         prefix, entry->start, entry->start + entry->size,
-                        entry->size, entry->free ? "free" : "used");
-                total += entry->size;
-                if (entry->free)
-                        total_free += entry->size;
-                else
-                        total_used += entry->size;
+                        entry->size);
+                total_used += entry->size;
+
+                if (entry->hole_follows) {
+                        hole_start = drm_mm_hole_node_start(entry);
+                        hole_end = drm_mm_hole_node_end(entry);
+                        hole_size = hole_end - hole_start;
+                        printk(KERN_DEBUG "%s 0x%08lx-0x%08lx: %8lu: free\n",
+                                prefix, hole_start, hole_end,
+                                hole_size);
+                        total_free += hole_size;
+                }
         }
-        printk(KERN_DEBUG "%s total: %d, used %d free %d\n", prefix, total,
+        total = total_free + total_used;
+
+        printk(KERN_DEBUG "%s total: %lu, used %lu free %lu\n", prefix, total,
                 total_used, total_free);
 }
 EXPORT_SYMBOL(drm_mm_debug_table);
@@ -641,17 +586,34 @@ EXPORT_SYMBOL(drm_mm_debug_table);
 int drm_mm_dump_table(struct seq_file *m, struct drm_mm *mm)
 {
         struct drm_mm_node *entry;
-        int total_used = 0, total_free = 0, total = 0;
-
-        list_for_each_entry(entry, &mm->node_list, node_list) {
-                seq_printf(m, "0x%08lx-0x%08lx: 0x%08lx: %s\n", entry->start, entry->start + entry->size, entry->size, entry->free ? "free" : "used");
-                total += entry->size;
-                if (entry->free)
-                        total_free += entry->size;
-                else
-                        total_used += entry->size;
+        unsigned long total_used = 0, total_free = 0, total = 0;
+        unsigned long hole_start, hole_end, hole_size;
+
+        hole_start = drm_mm_hole_node_start(&mm->head_node);
+        hole_end = drm_mm_hole_node_end(&mm->head_node);
+        hole_size = hole_end - hole_start;
+        if (hole_size)
+                seq_printf(m, "0x%08lx-0x%08lx: 0x%08lx: free\n",
+                                hole_start, hole_end, hole_size);
+        total_free += hole_size;
+
+        drm_mm_for_each_node(entry, mm) {
+                seq_printf(m, "0x%08lx-0x%08lx: 0x%08lx: used\n",
+                                entry->start, entry->start + entry->size,
+                                entry->size);
+                total_used += entry->size;
+                if (entry->hole_follows) {
+                        hole_start = drm_mm_hole_node_start(&mm->head_node);
+                        hole_end = drm_mm_hole_node_end(&mm->head_node);
+                        hole_size = hole_end - hole_start;
+                        seq_printf(m, "0x%08lx-0x%08lx: 0x%08lx: free\n",
+                                        hole_start, hole_end, hole_size);
+                        total_free += hole_size;
+                }
         }
-        seq_printf(m, "total: %d, used %d free %d\n", total, total_used, total_free);
+        total = total_free + total_used;
+
+        seq_printf(m, "total: %lu, used %lu free %lu\n", total, total_used, total_free);
         return 0;
 }
 EXPORT_SYMBOL(drm_mm_dump_table);
diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
index 0d791462f7b2..34fa36f2de70 100644
--- a/include/drm/drm_mm.h
+++ b/include/drm/drm_mm.h
@@ -42,23 +42,24 @@
 #endif
 
 struct drm_mm_node {
-        struct list_head free_stack;
         struct list_head node_list;
-        unsigned free : 1;
+        struct list_head hole_stack;
+        unsigned hole_follows : 1;
         unsigned scanned_block : 1;
         unsigned scanned_prev_free : 1;
         unsigned scanned_next_free : 1;
+        unsigned scanned_preceeds_hole : 1;
         unsigned long start;
         unsigned long size;
         struct drm_mm *mm;
 };
 
 struct drm_mm {
-        /* List of free memory blocks, most recently freed ordered. */
-        struct list_head free_stack;
-        /* List of all memory nodes, ordered according to the (increasing) start
-         * address of the memory node. */
-        struct list_head node_list;
+        /* List of all memory nodes that immediatly preceed a free hole. */
+        struct list_head hole_stack;
+        /* head_node.node_list is the list of all memory nodes, ordered
+         * according to the (increasing) start address of the memory node. */
+        struct drm_mm_node head_node;
         struct list_head unused_nodes;
         int num_unused;
         spinlock_t unused_lock;
@@ -74,9 +75,11 @@ struct drm_mm {
 
 static inline bool drm_mm_initialized(struct drm_mm *mm)
 {
-        return mm->free_stack.next;
+        return mm->hole_stack.next;
 }
-
+#define drm_mm_for_each_node(entry, mm) list_for_each_entry(entry, \
+                                                &(mm)->head_node.node_list, \
+                                                node_list);
 /*
  * Basic range manager support (drm_mm.c)
  */