Re: [PATCH 05/18] drm: Introduce an iterator over holes in the drm_mm range manager

Ben Widawsky
2012-11-05T13:40:42Z

On Fri, 19 Oct 2012 18:03:11 +0100
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> This will be used i915 in forthcoming patches in order to measure the
> largest contiguous chunk of memory available for enabling chipset
> features.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Dave Airlie <airlied@redhat.com>

nitpicks below
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

> ---
> drivers/gpu/drm/drm_mm.c | 55 +++++++++++++++-------------------------------
> include/drm/drm_mm.h | 26 ++++++++++++++++++++++
> 2 files changed, 44 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index 5db8c20..c3d11ec 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -102,20 +102,6 @@ int drm_mm_pre_get(struct drm_mm *mm)
> }
> EXPORT_SYMBOL(drm_mm_pre_get);
>
> -static inline unsigned long drm_mm_hole_node_start(struct drm_mm_node *hole_node)
> -{
> - return hole_node->start + hole_node->size;
> -}
> -
> -static inline unsigned long drm_mm_hole_node_end(struct drm_mm_node *hole_node)
> -{
> - struct drm_mm_node *next_node =
> - list_entry(hole_node->node_list.next, struct drm_mm_node,
> - node_list);
> -
> - return next_node->start;
> -}
> -
> static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
> struct drm_mm_node *node,
> unsigned long size, unsigned alignment,
> @@ -127,7 +113,7 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
> unsigned long adj_start = hole_start;
> unsigned long adj_end = hole_end;
>
> - BUG_ON(!hole_node->hole_follows || node->allocated);
> + BUG_ON(node->allocated);
>
> if (mm->color_adjust)
> mm->color_adjust(hole_node, color, &adj_start, &adj_end);
> @@ -168,15 +154,10 @@ struct drm_mm_node *drm_mm_create_block(struct drm_mm *mm,
> {
> struct drm_mm_node *hole, *node;
> unsigned long end = start + size;
> + unsigned long hole_start;
> + unsigned long hole_end;
>
> - list_for_each_entry(hole, &mm->hole_stack, hole_stack) {
> - unsigned long hole_start;
> - unsigned long hole_end;
> -
> - BUG_ON(!hole->hole_follows);
> - hole_start = drm_mm_hole_node_start(hole);
> - hole_end = drm_mm_hole_node_end(hole);
> -
> + drm_mm_for_each_hole(hole, mm, hole_start, hole_end) {
> if (hole_start > start || hole_end < end)
> continue;
>
> @@ -361,8 +342,10 @@ void drm_mm_remove_node(struct drm_mm_node *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));
> + BUG_ON(node->start + node->size !=
> + list_entry(node->node_list.next,
> + struct drm_mm_node, node_list)->start);
> +
>

This seems harder to read to me than before. I suspect you've changed it
only because you've moved the inline functions down, but I also don't
understand the reason for that.

> if (!prev_node->hole_follows) {
> prev_node->hole_follows = 1;
> @@ -420,6 +403,8 @@ struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
> {
> struct drm_mm_node *entry;
> struct drm_mm_node *best;
> + unsigned long adj_start;
> + unsigned long adj_end;
> unsigned long best_size;
>
> BUG_ON(mm->scanned_blocks);
> @@ -427,17 +412,13 @@ struct drm_mm_node *drm_mm_search_free_generic(const struct drm_mm *mm,
> best = NULL;
> best_size = ~0UL;
>
> - list_for_each_entry(entry, &mm->hole_stack, hole_stack) {
> - unsigned long adj_start = drm_mm_hole_node_start(entry);
> - unsigned long adj_end = drm_mm_hole_node_end(entry);
> -
> + drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
> if (mm->color_adjust) {
> mm->color_adjust(entry, color, &adj_start, &adj_end);
> if (adj_end <= adj_start)
> continue;
> }
>
> - BUG_ON(!entry->hole_follows);
> if (!check_free_hole(adj_start, adj_end, size, alignment))
> continue;
>
> @@ -464,6 +445,8 @@ struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_mm *mm,
> {
> struct drm_mm_node *entry;
> struct drm_mm_node *best;
> + unsigned long adj_start;
> + unsigned long adj_end;
> unsigned long best_size;
>
> BUG_ON(mm->scanned_blocks);
> @@ -471,13 +454,11 @@ struct drm_mm_node *drm_mm_search_free_in_range_generic(const struct drm_mm *mm,
> best = NULL;
> best_size = ~0UL;
>
> - 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);
> + drm_mm_for_each_hole(entry, mm, adj_start, adj_end) {
> + if (adj_start < start)
> + adj_start = start;
> + if (adj_end > end)
> + adj_end = end;
>
> if (mm->color_adjust) {
> mm->color_adjust(entry, color, &adj_start, &adj_end);
> diff --git a/include/drm/drm_mm.h b/include/drm/drm_mm.h
> index 4020f96..d710a10 100644
> --- a/include/drm/drm_mm.h
> +++ b/include/drm/drm_mm.h
> @@ -89,6 +89,19 @@ static inline bool drm_mm_initialized(struct drm_mm *mm)
> {
> return mm->hole_stack.next;
> }
> +
> +static inline unsigned long drm_mm_hole_node_start(struct drm_mm_node *hole_node)
> +{
> + BUG_ON(!hole_node->hole_follows);
> + return hole_node->start + hole_node->size;
> +}
> +
> +static inline unsigned long drm_mm_hole_node_end(struct drm_mm_node *hole_node)
> +{
> + return list_entry(hole_node->node_list.next,
> + struct drm_mm_node, node_list)->start;
> +}
> +
> #define drm_mm_for_each_node(entry, mm) list_for_each_entry(entry, \
> &(mm)->head_node.node_list, \
> node_list)
> @@ -99,6 +112,19 @@ static inline bool drm_mm_initialized(struct drm_mm *mm)
> entry != NULL; entry = next, \
> next = entry ? list_entry(entry->node_list.next, \
> struct drm_mm_node, node_list) : NULL) \
> +
> +/* Note that we need to unroll list_for_each_entry in order to inline
> + * setting hole_start and hole_end on each iteration and keep the
> + * macro sane.
> + */

This comment is probably better suited for the commit message then here
where it'd require git blame to make any sense of it.

> +#define drm_mm_for_each_hole(entry, mm, hole_start, hole_end) \
> + for (entry = list_entry((mm)->hole_stack.next, typeof(struct drm_mm_node), hole_stack); \
> + &entry->hole_stack != &(mm)->hole_stack ? \
> + hole_start = drm_mm_hole_node_start(entry), \
> + hole_end = drm_mm_hole_node_end(entry) : \
> + 0; \
> + entry = list_entry(entry->hole_stack.next, typeof(struct drm_mm_node), hole_stack))
> +
> /*
> * Basic range manager support (drm_mm.c)
> */

--
Ben Widawsky, Intel Open Source Technology Center