Merge series 'Use Maple Trees for simple_offset utilities' of https://lore.kernel.org/r/170820083431.6328.16233178852085891453.stgit@91.116.238.104.host.secureserver.net

Pull simple offset series from Chuck Lever

In an effort to address slab fragmentation issues reported a few
months ago, I've replaced the use of xarrays for the directory
offset map in "simple" file systems (including tmpfs).

Thanks to Liam Howlett for helping me get this working with Maple
Trees.

* series 'Use Maple Trees for simple_offset utilities' of https://lore.kernel.org/r/170820083431.6328.16233178852085891453.stgit@91.116.238.104.host.secureserver.net: (6 commits)
  libfs: Convert simple directory offsets to use a Maple Tree
  test_maple_tree: testing the cyclic allocation
  maple_tree: Add mtree_alloc_cyclic()
  libfs: Add simple_offset_empty()
  libfs: Define a minimum directory offset
  libfs: Re-arrange locking in offset_iterate_dir()

Signed-off-by: Christian Brauner <brauner@kernel.org>

2 files changed, 137 insertions, 0 deletions

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 6f241bb3879920..af097028872722 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4290,6 +4290,56 @@ exists:
 
 }
 
+/**
+ * mas_alloc_cyclic() - Internal call to find somewhere to store an entry
+ * @mas: The maple state.
+ * @startp: Pointer to ID.
+ * @range_lo: Lower bound of range to search.
+ * @range_hi: Upper bound of range to search.
+ * @entry: The entry to store.
+ * @next: Pointer to next ID to allocate.
+ * @gfp: The GFP_FLAGS to use for allocations.
+ *
+ * Return: 0 if the allocation succeeded without wrapping, 1 if the
+ * allocation succeeded after wrapping, or -EBUSY if there are no
+ * free entries.
+ */
+int mas_alloc_cyclic(struct ma_state *mas, unsigned long *startp,
+		void *entry, unsigned long range_lo, unsigned long range_hi,
+		unsigned long *next, gfp_t gfp)
+{
+	unsigned long min = range_lo;
+	int ret = 0;
+
+	range_lo = max(min, *next);
+	ret = mas_empty_area(mas, range_lo, range_hi, 1);
+	if ((mas->tree->ma_flags & MT_FLAGS_ALLOC_WRAPPED) && ret == 0) {
+		mas->tree->ma_flags &= ~MT_FLAGS_ALLOC_WRAPPED;
+		ret = 1;
+	}
+	if (ret < 0 && range_lo > min) {
+		ret = mas_empty_area(mas, min, range_hi, 1);
+		if (ret == 0)
+			ret = 1;
+	}
+	if (ret < 0)
+		return ret;
+
+	do {
+		mas_insert(mas, entry);
+	} while (mas_nomem(mas, gfp));
+	if (mas_is_err(mas))
+		return xa_err(mas->node);
+
+	*startp = mas->index;
+	*next = *startp + 1;
+	if (*next == 0)
+		mas->tree->ma_flags |= MT_FLAGS_ALLOC_WRAPPED;
+
+	return ret;
+}
+EXPORT_SYMBOL(mas_alloc_cyclic);
+
 static __always_inline void mas_rewalk(struct ma_state *mas, unsigned long index)
 {
 retry:
@@ -6443,6 +6493,49 @@ unlock:
 }
 EXPORT_SYMBOL(mtree_alloc_range);
 
+/**
+ * mtree_alloc_cyclic() - Find somewhere to store this entry in the tree.
+ * @mt: The maple tree.
+ * @startp: Pointer to ID.
+ * @range_lo: Lower bound of range to search.
+ * @range_hi: Upper bound of range to search.
+ * @entry: The entry to store.
+ * @next: Pointer to next ID to allocate.
+ * @gfp: The GFP_FLAGS to use for allocations.
+ *
+ * Finds an empty entry in @mt after @next, stores the new index into
+ * the @id pointer, stores the entry at that index, then updates @next.
+ *
+ * @mt must be initialized with the MT_FLAGS_ALLOC_RANGE flag.
+ *
+ * Context: Any context.  Takes and releases the mt.lock.  May sleep if
+ * the @gfp flags permit.
+ *
+ * Return: 0 if the allocation succeeded without wrapping, 1 if the
+ * allocation succeeded after wrapping, -ENOMEM if memory could not be
+ * allocated, -EINVAL if @mt cannot be used, or -EBUSY if there are no
+ * free entries.
+ */
+int mtree_alloc_cyclic(struct maple_tree *mt, unsigned long *startp,
+		void *entry, unsigned long range_lo, unsigned long range_hi,
+		unsigned long *next, gfp_t gfp)
+{
+	int ret;
+
+	MA_STATE(mas, mt, 0, 0);
+
+	if (!mt_is_alloc(mt))
+		return -EINVAL;
+	if (WARN_ON_ONCE(mt_is_reserved(entry)))
+		return -EINVAL;
+	mtree_lock(mt);
+	ret = mas_alloc_cyclic(&mas, startp, entry, range_lo, range_hi,
+			       next, gfp);
+	mtree_unlock(mt);
+	return ret;
+}
+EXPORT_SYMBOL(mtree_alloc_cyclic);
+
 int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
 		void *entry, unsigned long size, unsigned long min,
 		unsigned long max, gfp_t gfp)
diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index 29185ac5c727f6..399380db449cdd 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -3599,6 +3599,45 @@ static noinline void __init check_state_handling(struct maple_tree *mt)
 	mas_unlock(&mas);
 }
 
+static noinline void __init alloc_cyclic_testing(struct maple_tree *mt)
+{
+	unsigned long location;
+	unsigned long next;
+	int ret = 0;
+	MA_STATE(mas, mt, 0, 0);
+
+	next = 0;
+	mtree_lock(mt);
+	for (int i = 0; i < 100; i++) {
+		mas_alloc_cyclic(&mas, &location, mt, 2, ULONG_MAX, &next, GFP_KERNEL);
+		MAS_BUG_ON(&mas, i != location - 2);
+		MAS_BUG_ON(&mas, mas.index != location);
+		MAS_BUG_ON(&mas, mas.last != location);
+		MAS_BUG_ON(&mas, i != next - 3);
+	}
+
+	mtree_unlock(mt);
+	mtree_destroy(mt);
+	next = 0;
+	mt_init_flags(mt, MT_FLAGS_ALLOC_RANGE);
+	for (int i = 0; i < 100; i++) {
+		mtree_alloc_cyclic(mt, &location, mt, 2, ULONG_MAX, &next, GFP_KERNEL);
+		MT_BUG_ON(mt, i != location - 2);
+		MT_BUG_ON(mt, i != next - 3);
+		MT_BUG_ON(mt, mtree_load(mt, location) != mt);
+	}
+
+	mtree_destroy(mt);
+	/* Overflow test */
+	next = ULONG_MAX - 1;
+	ret = mtree_alloc_cyclic(mt, &location, mt, 2, ULONG_MAX, &next, GFP_KERNEL);
+	MT_BUG_ON(mt, ret != 0);
+	ret = mtree_alloc_cyclic(mt, &location, mt, 2, ULONG_MAX, &next, GFP_KERNEL);
+	MT_BUG_ON(mt, ret != 0);
+	ret = mtree_alloc_cyclic(mt, &location, mt, 2, ULONG_MAX, &next, GFP_KERNEL);
+	MT_BUG_ON(mt, ret != 1);
+}
+
 static DEFINE_MTREE(tree);
 static int __init maple_tree_seed(void)
 {
@@ -3880,6 +3919,11 @@ static int __init maple_tree_seed(void)
 	check_state_handling(&tree);
 	mtree_destroy(&tree);
 
+	mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
+	alloc_cyclic_testing(&tree);
+	mtree_destroy(&tree);
+
+
 #if defined(BENCH)
 skip:
 #endif