The patch titled
Subject: maple_tree: do not preallocate nodes for slot stores
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
maple_tree-do-not-preallocate-nodes-for-slot-stores.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-do-not-preallocate-nodes-for-slot-stores.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Subject: maple_tree: do not preallocate nodes for slot stores
Date: Tue, 12 Dec 2023 11:46:40 -0800
mas_preallocate() defaults to requesting 1 node for preallocation and then
,depending on the type of store, will update the request variable. There
isn't a check for a slot store type, so slot stores are preallocating the
default 1 node. Slot stores do not require any additional nodes, so add a
check for the slot store case that will bypass node_count_gfp(). Update
the tests to reflect that slot stores do not require allocations.
User visible effects of this bug include increased memory usage from the
unneeded node that was allocated.
Link: https://lkml.kernel.org/r/20231212194640.217966-1-sidhartha.kumar@xxxxxxxxxx
Fixes: 0b8bb544b1a7 ("maple_tree: update mas_preallocate() testing")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/maple_tree.c | 6 ++++++
tools/testing/radix-tree/maple.c | 2 +-
2 files changed, 7 insertions(+), 1 deletion(-)
--- a/lib/maple_tree.c~maple_tree-do-not-preallocate-nodes-for-slot-stores
+++ a/lib/maple_tree.c
@@ -5501,6 +5501,12 @@ int mas_preallocate(struct ma_state *mas
mas_wr_end_piv(&wr_mas);
node_size = mas_wr_new_end(&wr_mas);
+
+ /* Slot store, does not require additional nodes */
+ if ((node_size == mas->end) && ((!mt_in_rcu(mas->tree))
+ || (wr_mas.offset_end - mas->offset == 1)))
+ return 0;
+
if (node_size >= mt_slots[wr_mas.type]) {
/* Split, worst case for now. */
request = 1 + mas_mt_height(mas) * 2;
--- a/tools/testing/radix-tree/maple.c~maple_tree-do-not-preallocate-nodes-for-slot-stores
+++ a/tools/testing/radix-tree/maple.c
@@ -35538,7 +35538,7 @@ static noinline void __init check_preall
MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) != 0);
allocated = mas_allocated(&mas);
height = mas_mt_height(&mas);
- MT_BUG_ON(mt, allocated != 1);
+ MT_BUG_ON(mt, allocated != 0);
mas_store_prealloc(&mas, ptr);
MT_BUG_ON(mt, mas_allocated(&mas) != 0);
_
Patches currently in -mm which might be from sidhartha.kumar@xxxxxxxxxx are
maple_tree-do-not-preallocate-nodes-for-slot-stores.patch
