maple_tree: simplify mas_is_span_wr()

Make the code for detecting spanning writes more concise.

Link: https://lkml.kernel.org/r/20230524031247.65949-5-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 3fe6a66..41a105e 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3728,43 +3728,31 @@ static inline void mas_store_root(struct ma_state *mas, void *entry)
  */
 static bool mas_is_span_wr(struct ma_wr_state *wr_mas)
 {
-       unsigned long max;
+       unsigned long max = wr_mas->r_max;
        unsigned long last = wr_mas->mas->last;
-       unsigned long piv = wr_mas->r_max;
        enum maple_type type = wr_mas->type;
        void *entry = wr_mas->entry;
 
-       /* Contained in this pivot */
-       if (piv > last)
+       /* Contained in this pivot, fast path */
+       if (last < max)
                return false;
 
-       max = wr_mas->mas->max;
-       if (unlikely(ma_is_leaf(type))) {
-               /* Fits in the node, but may span slots. */
+       if (ma_is_leaf(type)) {
+               max = wr_mas->mas->max;
                if (last < max)
                        return false;
+       }
 
-               /* Writes to the end of the node but not null. */
-               if ((last == max) && entry)
-                       return false;
-
+       if (last == max) {
                /*
-                * Writing ULONG_MAX is not a spanning write regardless of the
-                * value being written as long as the range fits in the node.
+                * The last entry of leaf node cannot be NULL unless it is the
+                * rightmost node (writing ULONG_MAX), otherwise it spans slots.
                 */
-               if ((last == ULONG_MAX) && (last == max))
-                       return false;
-       } else if (piv == last) {
-               if (entry)
-                       return false;
-
-               /* Detect spanning store wr walk */
-               if (last == ULONG_MAX)
+               if (entry || last == ULONG_MAX)
                        return false;
        }
 
-       trace_ma_write(__func__, wr_mas->mas, piv, entry);
-
+       trace_ma_write(__func__, wr_mas->mas, wr_mas->r_max, entry);
        return true;
 }