+ maple_tree-avoid-extra-gap-calculation.patch added to mm-unstable branch

The patch titled
     Subject: maple_tree: avoid extra gap calculation
has been added to the -mm mm-unstable branch.  Its filename is
     maple_tree-avoid-extra-gap-calculation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-avoid-extra-gap-calculation.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: "Liam R. Howlett (Oracle)" <[email protected]>
Subject: maple_tree: avoid extra gap calculation
Date: Fri, 21 Aug 2026 15:26:26 -0400

Prior to ending the ascension loop of larger operations like split,
rebalance, and spanning store the gap in the node had been calculated. 
Once the node is inserted into the tree, the gap is recalculated in
mas_update_gap().  This can be avoided by creating a helper for
mas_update_gap() that accepts the known gap value, which reduces the
operations required for gap updating path.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Liam R. Howlett (Oracle) <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Breno Leitao <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Chuck Lever <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 lib/maple_tree.c |   28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

--- a/lib/maple_tree.c~maple_tree-avoid-extra-gap-calculation
+++ a/lib/maple_tree.c
@@ -1566,14 +1566,26 @@ ascend:
 	goto ascend;
 }
 
+static __always_inline void mas_update_gap_known(struct ma_state *mas,
+		unsigned long gap)
+{
+	unsigned char pslot;
+	unsigned long p_gap;
+
+	pslot = mte_parent_slot(mas->node);
+	p_gap = ma_gaps(mte_parent(mas->node),
+			mas_parent_type(mas, mas->node))[pslot];
+
+	if (p_gap != gap)
+		mas_parent_gap(mas, pslot, gap);
+}
+
 /*
  * mas_update_gap() - Update a nodes gaps and propagate up if necessary.
  * @mas: the maple state.
  */
 static inline void mas_update_gap(struct ma_state *mas)
 {
-	unsigned char pslot;
-	unsigned long p_gap;
 	unsigned long max_gap;
 
 	if (!mt_is_alloc(mas->tree))
@@ -1583,13 +1595,7 @@ static inline void mas_update_gap(struct
 		return;
 
 	max_gap = mas_max_gap(mas);
-
-	pslot = mte_parent_slot(mas->node);
-	p_gap = ma_gaps(mte_parent(mas->node),
-			mas_parent_type(mas, mas->node))[pslot];
-
-	if (p_gap != max_gap)
-		mas_parent_gap(mas, pslot, max_gap);
+	mas_update_gap_known(mas, max_gap);
 }
 
 /*
@@ -2137,8 +2143,8 @@ static inline void mas_wmb_replace(struc
 	mas->node = mt_slot_locked(mas->tree, cp->slot, 0);
 	/* Insert the new data in the tree */
 	mas_topiary_replace(mas, old_enode, cp->height);
-	if (!mte_is_leaf(mas->node))
-		mas_update_gap(mas);
+	if (mt_is_alloc(mas->tree) && !mte_is_root(mas->node))
+		mas_update_gap_known(mas, cp->gap[0]);
 
 	mtree_range_walk(mas);
 }
_

Patches currently in -mm which might be from [email protected] are

maple_tree-add-rcu-locking-check-when-lockdep-is-enabled.patch
locking-lockdep-add-sequence-counter-to-held_lock.patch
maple_tree-add-write-lock-checking-with-lockdep-sequence-numbers.patch
maple_tree-documentation-fix.patch
maple_tree-drop-dead-code-from-mas_extend_spanning_null.patch
maple_tree-drop-maple_alloc_slots.patch
maple_tree-clarify-comments-on-mas_nomem.patch
maple_tree-use-prefetched-value-in-mas_wr_store_type.patch
maple_tree-optimise-mas_wr_node_store-when-not-in-rcu-mode.patch
maple_tree-micro-optimisation-of-mas_wr_store_type.patch
maple_tree-add-bulk-parent-set-helper.patch
maple_tree-catch-race-in-mas_alloc_cyclic.patch
maple_tree-document-that-erase-may-use-gfp_kernel-for-allocations.patch
maple_tree-avoid-mas_erase-and-mtree_erase-failures.patch
maple_tree-document-erase-and-allocations-better.patch
maple_tree-change-two-gfp-flags-in-tests.patch
maple_tree-fix-argument-name-in-header.patch
maple_tree-avoid-extra-gap-calculation.patch
maple_tree-add-helper-mas_make_walkable.patch