From: Matthew Wilcox <willy@infradead.org>
Date: Wed, 5 Dec 2018 19:48:03 +0000 (-0500)
Subject: maple_tree: Fix nomem bug
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=cf149a320e85b4ca3ad20a8bd00ac395c396fb34;p=users%2Fjedix%2Flinux-maple.git

maple_tree: Fix nomem bug

Add a pair of tests to check that -ENOMEM works correctly, and fix a
bug in __maple_nomem() which was inadvertently clearing the error
mark in the case of a second memory allocation failure.  Also add an
implemenation of mtree_empty().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---

diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index dd7d428db032..00892c978e37 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -179,4 +179,16 @@ int mtree_erase(struct maple_tree *mt, unsigned long index);
 
 int mtree_destroy(struct maple_tree *mt);
 
+/**
+ * mtree_empty() - Determine if a tree has any present entries.
+ * @mt: Maple Tree.
+ *
+ * Context: Any context.
+ * Return: %true if the array contains only NULL pointers.
+ */
+static inline bool mtree_empty(const struct maple_tree *mt)
+{
+	return mt->root == NULL;
+}
+
 #endif
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index bdece8c955d3..e64bdaf61baa 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -168,9 +168,9 @@ static bool __maple_nomem(struct maple_state *ms, gfp_t gfp)
 	} else {
 		maple_new_node(ms, ma_get_alloc_cnt(ms), gfp);
 	}
-	ms->node = MAS_START;
 	if (!ma_get_alloc(ms))
 		return false;
+	ms->node = MAS_START;
 	return true;
 }
 
diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index 543d3db12ce8..d7a4ec038575 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -30,12 +30,18 @@ void mt_dump(const struct maple_tree *mt) { }
 } while (0)
 #endif
 
+static
+int mtree_insert_index(struct maple_tree *mt, unsigned long index, gfp_t gfp)
+{
+	return mtree_insert(mt, index, xa_mk_value(index & LONG_MAX), gfp);
+}
 
 static int mtree_test_insert(struct maple_tree *mt, unsigned long index,
 				void *ptr)
 {
 	return mtree_insert(mt, index, ptr, GFP_KERNEL);
 }
+
 static int mtree_test_insert_range(struct maple_tree *mt, unsigned long start,
 				unsigned long end, void *ptr)
 {
@@ -81,6 +87,18 @@ static noinline void check_load(struct maple_tree *mt, unsigned long index,
 	MT_BUG_ON(mt, ret != ptr);
 }
 
+static noinline void check_nomem(struct maple_tree *mt)
+{
+	MT_BUG_ON(mt, !mtree_empty(mt));
+
+	/* Storing something at 1 requires memory allocation */
+	MT_BUG_ON(mt, mtree_insert_index(mt, 1, GFP_ATOMIC) != -ENOMEM);
+	/* Storing something at 0 does not */
+	MT_BUG_ON(mt, mtree_insert_index(mt, 0, GFP_ATOMIC) != 0);
+
+	mtree_destroy(mt);
+}
+
 static DEFINE_MAPLE_TREE(tree);
 
 static int maple_tree_seed(void)
@@ -200,8 +218,8 @@ static int maple_tree_seed(void)
 	check_load(&tree, set[9], &tree);
 	mtree_destroy(&tree);
 
+	check_nomem(&tree);
 
-	
 	printk("maple_tree: %u of %u tests passed\n", tests_passed, tests_run);
 	return (tests_run == tests_passed) ? 0 : -EINVAL;
 }