crush: merge working data and scratch

Much like Arlo Guthrie, I decided that one big pile is better than two
little piles.

Reflects ceph.git commit 95c2df6c7e0b22d2ea9d91db500cf8b9441c73ba.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/include/linux/crush/mapper.h b/include/linux/crush/mapper.h
index 3303c7fd8a31..c95e19e1ff11 100644
--- a/include/linux/crush/mapper.h
+++ b/include/linux/crush/mapper.h
@@ -15,7 +15,19 @@ extern int crush_do_rule(const struct crush_map *map,
                          int ruleno,
                          int x, int *result, int result_max,
                          const __u32 *weights, int weight_max,
-                         void *cwin, int *scratch);
+                         void *cwin);
+
+/*
+ * Returns the exact amount of workspace that will need to be used
+ * for a given combination of crush_map and result_max. The caller can
+ * then allocate this much on its own, either on the stack, in a
+ * per-thread long-lived buffer, or however it likes.
+ */
+static inline size_t crush_work_size(const struct crush_map *map,
+                                     int result_max)
+{
+        return map->working_size + result_max * 3 * sizeof(__u32);
+}
 
 void crush_init_workspace(const struct crush_map *map, void *v);