On 12/12/23 11:52 AM, Sidhartha Kumar wrote:
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.
Fixes: 0b8bb544b1a7 ("maple_tree: update mas_preallocate() testing")
Cc: <stable@xxxxxxxxxxxxxxx> # 6.6+
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
---
This is a modified backport as the patch to fix this in upstream does not
apply to 6.6 because the node_end field was moved from the ma_wr_state to
the ma_state after 6.6.
Please disregard this patch, the upstream fix[1] does actually apply correctly
to the 6.6 stable branch.
Sorry for the noise,
Sid
[1]
https://lore.kernel.org/linux-mm/20231213205058.386589-1-sidhartha.kumar@xxxxxxxxxx/T/#u
lib/maple_tree.c | 6 ++++++
tools/testing/radix-tree/maple.c | 2 +-
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index bb24d84a4922f..5950d0c0e0f69 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5501,6 +5501,12 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
mas_wr_end_piv(&wr_mas);
node_size = mas_wr_new_end(&wr_mas);
+
+ /* Slot store, does not require additional nodes */
+ if ((node_size == wr_mas.node_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;
diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index e5da1cad70baf..76a8990bb14e8 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -35538,7 +35538,7 @@ static noinline void __init check_prealloc(struct maple_tree *mt)
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);
