[PATCH v6 3/3] drm/buddy: Add defragmentation support

[Arunpravin Paneer Selvam]

Add a function to support defragmentation.

v1: Defragment the memory beginning from min_order
    till the required memory space is available.

Signed-off-by: Arunpravin Paneer Selvam <arunpravin.paneersel...@amd.com>
Suggested-by: Matthew Auld <matthew.a...@intel.com>
---
 drivers/gpu/drm/drm_buddy.c | 67 +++++++++++++++++++++++++++++++------
 include/drm/drm_buddy.h     |  3 ++
 2 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 33ad0cfbd54c..fac423d2cb73 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -276,10 +276,12 @@ drm_get_buddy(struct drm_buddy_block *block)
 }
 EXPORT_SYMBOL(drm_get_buddy);
 
-static void __drm_buddy_free(struct drm_buddy *mm,
-                            struct drm_buddy_block *block)
+static unsigned int __drm_buddy_free(struct drm_buddy *mm,
+                                    struct drm_buddy_block *block,
+                                    bool defrag)
 {
        struct drm_buddy_block *parent;
+       unsigned int order;
 
        while ((parent = block->parent)) {
                struct drm_buddy_block *buddy;
@@ -289,12 +291,14 @@ static void __drm_buddy_free(struct drm_buddy *mm,
                if (!drm_buddy_block_is_free(buddy))
                        break;
 
-               if (drm_buddy_block_is_clear(block) !=
-                   drm_buddy_block_is_clear(buddy))
-                       break;
+               if (!defrag) {
+                       if (drm_buddy_block_is_clear(block) !=
+                           drm_buddy_block_is_clear(buddy))
+                               break;
 
-               if (drm_buddy_block_is_clear(block))
-                       mark_cleared(parent);
+                       if (drm_buddy_block_is_clear(block))
+                               mark_cleared(parent);
+               }
 
                list_del(&buddy->link);
 
@@ -304,8 +308,49 @@ static void __drm_buddy_free(struct drm_buddy *mm,
                block = parent;
        }
 
+       order = drm_buddy_block_order(block);
        mark_free(mm, block);
+
+       return order;
+}
+
+/**
+ * drm_buddy_defrag - Defragmentation routine
+ *
+ * @mm: DRM buddy manager
+ * @min_order: minimum order in the freelist to begin
+ * the defragmentation process
+ *
+ * Driver calls the defragmentation function when the
+ * requested memory allocation returns -ENOSPC.
+ */
+void drm_buddy_defrag(struct drm_buddy *mm,
+                     unsigned int min_order)
+{
+       struct drm_buddy_block *block;
+       struct list_head *list;
+       unsigned int order;
+       int i;
+
+       if (min_order > mm->max_order)
+               return;
+
+       for (i = min_order - 1; i >= 0; i--) {
+               list = &mm->free_list[i];
+               if (list_empty(list))
+                       continue;
+
+               list_for_each_entry_reverse(block, list, link) {
+                       if (!block->parent)
+                               continue;
+
+                       order = __drm_buddy_free(mm, block, 1);
+                       if (order >= min_order)
+                               return;
+               }
+       }
 }
+EXPORT_SYMBOL(drm_buddy_defrag);
 
 /**
  * drm_buddy_free_block - free a block
@@ -321,7 +366,7 @@ void drm_buddy_free_block(struct drm_buddy *mm,
        if (drm_buddy_block_is_clear(block))
                mm->clear_avail += drm_buddy_block_size(mm, block);
 
-       __drm_buddy_free(mm, block);
+       __drm_buddy_free(mm, block, 0);
 }
 EXPORT_SYMBOL(drm_buddy_free_block);
 
@@ -470,7 +515,7 @@ __alloc_range_bias(struct drm_buddy *mm,
        if (buddy &&
            (drm_buddy_block_is_free(block) &&
             drm_buddy_block_is_free(buddy)))
-               __drm_buddy_free(mm, block);
+               __drm_buddy_free(mm, block, 0);
        return ERR_PTR(err);
 }
 
@@ -588,7 +633,7 @@ alloc_from_freelist(struct drm_buddy *mm,
 
 err_undo:
        if (tmp != order)
-               __drm_buddy_free(mm, block);
+               __drm_buddy_free(mm, block, 0);
        return ERR_PTR(err);
 }
 
@@ -668,7 +713,7 @@ static int __alloc_range(struct drm_buddy *mm,
        if (buddy &&
            (drm_buddy_block_is_free(block) &&
             drm_buddy_block_is_free(buddy)))
-               __drm_buddy_free(mm, block);
+               __drm_buddy_free(mm, block, 0);
 
 err_free:
        if (err == -ENOSPC && total_allocated_on_err) {
diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index d81c596dfa38..d0f63e7b5915 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -166,6 +166,9 @@ void drm_buddy_free_list(struct drm_buddy *mm,
                         struct list_head *objects,
                         unsigned int flags);
 
+void drm_buddy_defrag(struct drm_buddy *mm,
+                     unsigned int min_order);
+
 void drm_buddy_print(struct drm_buddy *mm, struct drm_printer *p);
 void drm_buddy_block_print(struct drm_buddy *mm,
                           struct drm_buddy_block *block,
-- 
2.25.1