maple_tree: introduce mas_wr_store_type()

Introduce mas_wr_store_type() which will set the correct store type based
on a walk of the tree.  In mas_wr_node_store() the <= min_slots condition
is changed to < as if new_end is = to mt_min_slots then there is not
enough room.

mas_prealloc_calc() is also introduced to abstract the calculation used to
determine the number of nodes needed for a store operation.

In this change a call to mas_reset() is removed in the error case of
mas_prealloc().  This is only needed in the MA_STATE_REBALANCE case of
mas_destroy().  We can move the call to mas_reset() directly to
mas_destroy().

Also, add a test case to validate the order that we check the store type
in is correct.  This test models a vma expanding and then shrinking which
is part of the boot process.

Link: https://lkml.kernel.org/r/20240814161944.55347-5-sidhartha.kumar@oracle.com
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: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index ef5b83cf94ea..ad42a36231fb 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -36283,6 +36283,38 @@ static void check_nomem_writer_race(struct maple_tree *mt)
 	mtree_unlock(mt);
 }
 
+ /* test to simulate expanding a vma from [0x7fffffffe000, 0x7ffffffff000)
+  * to [0x7ffde4ca1000, 0x7ffffffff000) and then shrinking the vma to
+  * [0x7ffde4ca1000, 0x7ffde4ca2000)
+  */
+static inline int check_vma_modification(struct maple_tree *mt)
+{
+	MA_STATE(mas, mt, 0, 0);
+
+	mtree_lock(mt);
+	/* vma with old start and old end */
+	__mas_set_range(&mas, 0x7fffffffe000, 0x7ffffffff000 - 1);
+	mas_preallocate(&mas, xa_mk_value(1), GFP_KERNEL);
+	mas_store_prealloc(&mas, xa_mk_value(1));
+
+	/* next write occurs partly in previous range [0, 0x7fffffffe000)*/
+	mas_prev_range(&mas, 0);
+	/* expand vma to {0x7ffde4ca1000, 0x7ffffffff000) */
+	__mas_set_range(&mas, 0x7ffde4ca1000, 0x7ffffffff000 - 1);
+	mas_preallocate(&mas, xa_mk_value(1), GFP_KERNEL);
+	mas_store_prealloc(&mas, xa_mk_value(1));
+
+	/* shrink vma to [0x7ffde4ca1000, 7ffde4ca2000) */
+	__mas_set_range(&mas, 0x7ffde4ca2000, 0x7ffffffff000 - 1);
+	mas_preallocate(&mas, NULL, GFP_KERNEL);
+	mas_store_prealloc(&mas, NULL);
+	mt_dump(mt, mt_dump_hex);
+
+	mas_destroy(&mas);
+	mtree_unlock(mt);
+	return 0;
+}
+
 void farmer_tests(void)
 {
 	struct maple_node *node;
@@ -36290,6 +36322,10 @@ void farmer_tests(void)
 
 	mt_dump(&tree, mt_dump_dec);
 
+	mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN | MT_FLAGS_USE_RCU);
+	check_vma_modification(&tree);
+	mtree_destroy(&tree);
+
 	tree.ma_root = xa_mk_value(0);
 	mt_dump(&tree, mt_dump_dec);