maple_tree: do not preallocate nodes for slot stores

commit 4249f13c11be8b8b7bf93204185e150c3bdc968d upstream.

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/20231213205058.386589-1-sidhartha.kumar@oracle.com
Fixes: 0b8bb544b1a7 ("maple_tree: update mas_preallocate() testing")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: <stable@vger.kernel.org>	[6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index bb24d84..6846894 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5501,6 +5501,17 @@ 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) {
+               /* reuse node */
+               if (!mt_in_rcu(mas->tree))
+                       return 0;
+               /* shifting boundary */
+               if (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 e5da1ca..76a8990 100644 (file)
--- 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);