maple_tree: add cp_is_new_root() helper

Add a helper to do what is needed when the maple copy node contains a new
root node.  This is useful for future commits and is self-documenting
code.

[Liam.Howlett@oracle.com: remove warnings on older compilers]
Link: https://lkml.kernel.org/r/malwmirqnpuxqkqrobcmzfkmmxipoyzwfs2nwc5fbpxlt2r2ej@wchmjtaljvw3
[akpm@linux-foundation.org: s/cp->slot[0]/&cp->slot[0]/, per Liam]
Link: https://lkml.kernel.org/r/20260130205935.2559335-22-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andrew Ballance <andrewjballance@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 2383c97f684b1aeda8cfdbb95c5c641b760881ce..6a8f75dac6c9e8dba9ca2de074501785272b822f 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3337,6 +3337,43 @@ static void mas_spanning_rebalance(struct ma_state *mas,
        mas_spanning_rebalance_loop(mas, mast, count);
 }
 
+static inline bool cp_is_new_root(struct maple_copy *cp, struct ma_state *mas)
+{
+       if (cp->min || cp->max != ULONG_MAX)
+               return false;
+
+       if (cp->d_count != 1) {
+               enum maple_type mt = maple_arange_64;
+
+               if (!mt_is_alloc(mas->tree))
+                       mt = maple_range_64;
+
+               cp->data = cp->d_count;
+               cp->s_count = 0;
+               dst_setup(cp, mas, mt);
+               init_cp_src(cp);
+               node_copy(mas, cp->src[0].node, 0, cp->data, cp->max, maple_copy,
+                         cp->dst[0].node, 0, mt);
+               node_finalise(cp->dst[0].node, mt, cp->end + 1);
+               /*
+                * Warning, see cp_leaf_init() comment and rcu_assign_pointer()
+                * documentation.  Since this is a new root, there are no
+                * read-side operations that can view it until it is insert into
+                * the tree after an rcu_assign_pointer() call.
+                */
+               ma_init_slot(&cp->slot[0], cp->dst[0].node, mt);
+               cp->height++;
+       }
+       WARN_ON_ONCE(cp->dst[0].node != mte_to_node(
+                               mt_slot_locked(mas->tree, cp->slot, 0)));
+       cp->dst[0].node->parent = ma_parent_ptr(mas_tree_parent(mas));
+       mas->min = 0;
+       mas->max = ULONG_MAX;
+       mas->depth = 0;
+       mas->node = mas_root_locked(mas);
+       return true;
+}
+
 /*
  * spanning_ascend() - See if a spanning store operation has to keep walking up
  * the tree
@@ -3359,39 +3396,8 @@ static bool spanning_ascend(struct maple_copy *cp, struct ma_state *mas,
        }
 
        cp_dst_to_slots(cp, l_wr_mas->mas->min, r_wr_mas->mas->max, mas);
-       if (!cp->min && cp->max == ULONG_MAX) {
-               /* New root */
-               if (cp->d_count != 1) {
-                       enum maple_type mt = maple_arange_64;
-
-                       if (!mt_is_alloc(mas->tree))
-                               mt = maple_range_64;
-
-                       cp->data = cp->d_count;
-                       cp->s_count = 0;
-                       dst_setup(cp, mas, mt);
-                       init_cp_src(cp);
-                       node_copy(mas, cp->src[0].node, 0, cp->data, cp->max, maple_copy,
-                                 cp->dst[0].node, 0, mt);
-                       node_finalise(cp->dst[0].node, mt, cp->end + 1);
-                       /*
-                        * Warning, see cp_leaf_init() comment and rcu_assign_pointer()
-                        * documentation.  Since this is a new root, there are no
-                        * read-side operations that can view it until it is insert into
-                        * the tree after an rcu_assign_pointer() call.
-                        */
-                       ma_init_slot(&cp->slot[0], cp->dst[0].node, mt);
-                       cp->height++;
-               }
-               WARN_ON_ONCE(cp->dst[0].node != mte_to_node(
-                               mt_slot_locked(mas->tree, cp->slot, 0)));
-               cp->dst[0].node->parent = ma_parent_ptr(mas_tree_parent(mas));
-               mas->min = 0;
-               mas->max = ULONG_MAX;
-               mas->depth = 0;
-               mas->node = mas_root_locked(mas);
+       if (cp_is_new_root(cp, mas))
                return false;
-       }
 
        /* Converged and has a single destination */
        if ((cp->d_count == 1) &&