maple_tree: add cp_converged() helper

When the maple copy node converges into a single entry, then certain
operations can stop ascending the tree.

This is used more later.

Link: https://lkml.kernel.org/r/20260130205935.2559335-26-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>

1 files changed, 11 insertions, 3 deletions

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 86072bfc2419..3e0469d365e6 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3493,6 +3493,16 @@ static inline bool cp_is_new_root(struct maple_copy *cp, struct ma_state *mas)
 	return true;
 }
 
+static inline bool cp_converged(struct maple_copy *cp, struct ma_state *mas,
+				struct ma_state *sib)
+{
+	if (cp->d_count != 1 || sib->end)
+		return false;
+
+	cp->dst[0].node->parent = ma_parent_ptr(mas_mn(mas)->parent);
+	return true;
+}
+
 /*
  * spanning_ascend() - See if a spanning store operation has to keep walking up
  * the tree
@@ -3575,10 +3585,8 @@ static inline bool rebalance_ascend(struct maple_copy *cp,
 	if (cp_is_new_root(cp, mas))
 		return false;
 
-	if (cp->d_count == 1 && !sib->end) {
-		cp->dst[0].node->parent = ma_parent_ptr(mas_mn(mas)->parent);
+	if (cp_converged(cp, mas, sib))
 		return false;
-	}
 
 	cp->height++;
 	copy_tree_location(parent, mas);