[PATCH] drm: mm: fix range restricted allocations

[Daniel Vetter]

With the code cleanup in

7a6b2896f261894dde287d3faefa4b432cddca53 is the first bad commit
commit 7a6b2896f261894dde287d3faefa4b432cddca53
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Fri Jul 2 15:02:15 2010 +0100

    drm_mm: extract check_free_mm_node

I've botched up the range-restriction checks. The result is usually
an X server dying with SIGBUS in libpixman (software fallback rendering).
Change the code to adjust the start and end for range restricted
allocations. IMHO this even makes the code a bit clearer.

Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/drm_mm.c |   24 ++++++++++++++----------
 1 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index da99edc..a6bfc30 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -285,21 +285,21 @@ void drm_mm_put_block(struct drm_mm_node *cur)

 EXPORT_SYMBOL(drm_mm_put_block);

-static int check_free_mm_node(struct drm_mm_node *entry, unsigned long size,
-                             unsigned alignment)
+static int check_free_hole(unsigned long start, unsigned long end,
+                          unsigned long size, unsigned alignment)
 {
        unsigned wasted = 0;

-       if (entry->size < size)
+       if (end - start < size)
                return 0;

        if (alignment) {
-               register unsigned tmp = entry->start % alignment;
+               unsigned tmp = start % alignment;
                if (tmp)
                        wasted = alignment - tmp;
        }

-       if (entry->size >= size + wasted) {
+       if (end >= start + size + wasted) {
                return 1;
        }

@@ -320,7 +320,8 @@ struct drm_mm_node *drm_mm_search_free(const struct drm_mm 
*mm,
        best_size = ~0UL;

        list_for_each_entry(entry, &mm->free_stack, free_stack) {
-               if (!check_free_mm_node(entry, size, alignment))
+               if (!check_free_hole(entry->start, entry->start + entry->size,
+                                    size, alignment))
                        continue;

                if (!best_match)
@@ -353,10 +354,12 @@ struct drm_mm_node *drm_mm_search_free_in_range(const 
struct drm_mm *mm,
        best_size = ~0UL;

        list_for_each_entry(entry, &mm->free_stack, free_stack) {
-               if (entry->start > end || (entry->start+entry->size) < start)
-                       continue;
+               unsigned long adj_start = entry->start < start ?
+                       start : entry->start;
+               unsigned long adj_end = entry->start + entry->size > end ?
+                       end : entry->start + entry->size;

-               if (!check_free_mm_node(entry, size, alignment))
+               if (!check_free_hole(adj_start, adj_end, size, alignment))
                        continue;

                if (!best_match)
@@ -449,7 +452,8 @@ int drm_mm_scan_add_block(struct drm_mm_node *node)
        node->free_stack.prev = prev_free;
        node->free_stack.next = next_free;

-       if (check_free_mm_node(node, mm->scan_size, mm->scan_alignment)) {
+       if (check_free_hole(node->start, node->start + node->size,
+                           mm->scan_size, mm->scan_alignment)) {
                mm->scan_hit_start = node->start;
                mm->scan_hit_size = node->size;

-- 
1.7.1