maple_tree: check for MA_STATE_BULK on setting wr_rebalance

It is possible for a bulk operation (MA_STATE_BULK is set) to enter the
new_end < mt_min_slots[type] case and set wr_rebalance as a store type.
This is incorrect as bulk stores do not rebalance per write, but rather
after the all of the writes are done through the mas_bulk_rebalance()
path.  Therefore, add a check to make sure MA_STATE_BULK is not set before
we return wr_rebalance as the store type.

Also add a test to make sure wr_rebalance is never the store type when
doing bulk operations via mas_expected_entries()

This is a hotfix for this rc however it has no userspace effects as there
are no users of the bulk insertion mode.

Link: https://lkml.kernel.org/r/20241011214451.7286-1-sidhartha.kumar@oracle.com
Fixes: 5d659bbb52a2 ("maple_tree: introduce mas_wr_store_type()")
Suggested-by: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Sidhartha <sidhartha.kumar@oracle.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 20990ec..ce7c7a7 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4218,7 +4218,7 @@ static inline void mas_wr_store_type(struct ma_wr_state *wr_mas)
 
        /* Potential spanning rebalance collapsing a node */
        if (new_end < mt_min_slots[wr_mas->type]) {
-               if (!mte_is_root(mas->node)) {
+               if (!mte_is_root(mas->node) && !(mas->mas_flags & MA_STATE_BULK)) {
                        mas->store_type = wr_rebalance;
                        return;
                }

diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index 1873ddb..6ec1888 100644 (file)
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -36317,6 +36317,28 @@ static inline int check_vma_modification(struct maple_tree *mt)
        return 0;
 }
 
+/*
+ * test to check that bulk stores do not use wr_rebalance as the store
+ * type.
+ */
+static inline void check_bulk_rebalance(struct maple_tree *mt)
+{
+       MA_STATE(mas, mt, ULONG_MAX, ULONG_MAX);
+       int max = 10;
+
+       build_full_tree(mt, 0, 2);
+
+       /* erase every entry in the tree */
+       do {
+               /* set up bulk store mode */
+               mas_expected_entries(&mas, max);
+               mas_erase(&mas);
+               MT_BUG_ON(mt, mas.store_type == wr_rebalance);
+       } while (mas_prev(&mas, 0) != NULL);
+
+       mas_destroy(&mas);
+}
+
 void farmer_tests(void)
 {
        struct maple_node *node;
@@ -36328,6 +36350,10 @@ void farmer_tests(void)
        check_vma_modification(&tree);
        mtree_destroy(&tree);
 
+       mt_init(&tree);
+       check_bulk_rebalance(&tree);
+       mtree_destroy(&tree);
+
        tree.ma_root = xa_mk_value(0);
        mt_dump(&tree, mt_dump_dec);