dm array: add dm_array_new()

dm_array_new() creates a new, populated array more efficiently than
starting with an empty one and resizing.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/persistent-data/dm-array.c

@@ -277,32 +277,13 @@ static int insert_ablock(struct dm_array_info *info, uint64_t index,
 	return dm_btree_insert(&info->btree_info, *root, &index, &block_le, root);
 }
 
-/*
- * Looks up an array block in the btree.  Then shadows it, and updates the
- * btree to point to this new shadow.  'root' is an input/output parameter
- * for both the current root block, and the new one.
- */
-static int shadow_ablock(struct dm_array_info *info, dm_block_t *root,
-			 unsigned index, struct dm_block **block,
-			 struct array_block **ab)
-{
-	int r, inc;
-	uint64_t key = index;
-	dm_block_t b;
-	__le64 block_le;
-
-	/*
-	 * lookup
-	 */
-	r = dm_btree_lookup(&info->btree_info, *root, &key, &block_le);
-	if (r)
-		return r;
-	b = le64_to_cpu(block_le);
+/*----------------------------------------------------------------*/
 
-	/*
-	 * shadow
-	 */
-	r = dm_tm_shadow_block(info->btree_info.tm, b,
+static int __shadow_ablock(struct dm_array_info *info, dm_block_t b,
+			   struct dm_block **block, struct array_block **ab)
+{
+	int inc;
+	int r = dm_tm_shadow_block(info->btree_info.tm, b,
 				   &array_validator, block, &inc);
 	if (r)
 		return r;
@@ -311,13 +292,20 @@ static int shadow_ablock(struct dm_array_info *info, dm_block_t *root,
 	if (inc)
 		inc_ablock_entries(info, *ab);
 
-	/*
-	 * Reinsert.
-	 *
+	return 0;
+}
+
+/*
  * The shadow op will often be a noop.  Only insert if it really
  * copied data.
  */
-	if (dm_block_location(*block) != b) {
+static int __reinsert_ablock(struct dm_array_info *info, unsigned index,
+			     struct dm_block *block, dm_block_t b,
+			     dm_block_t *root)
+{
+	int r = 0;
+
+	if (dm_block_location(block) != b) {
 		/*
 		 * dm_tm_shadow_block will have already decremented the old
 		 * block, but it is still referenced by the btree.  We
@@ -325,12 +313,38 @@ static int shadow_ablock(struct dm_array_info *info, dm_block_t *root,
 		 * when overwriting the old value.
 		 */
 		dm_tm_inc(info->btree_info.tm, b);
-		r = insert_ablock(info, index, *block, root);
+		r = insert_ablock(info, index, block, root);
 	}
 
 	return r;
 }
 
+/*
+ * Looks up an array block in the btree.  Then shadows it, and updates the
+ * btree to point to this new shadow.  'root' is an input/output parameter
+ * for both the current root block, and the new one.
+ */
+static int shadow_ablock(struct dm_array_info *info, dm_block_t *root,
+			 unsigned index, struct dm_block **block,
+			 struct array_block **ab)
+{
+	int r;
+	uint64_t key = index;
+	dm_block_t b;
+	__le64 block_le;
+
+	r = dm_btree_lookup(&info->btree_info, *root, &key, &block_le);
+	if (r)
+		return r;
+	b = le64_to_cpu(block_le);
+
+	r = __shadow_ablock(info, b, block, ab);
+	if (r)
+		return r;
+
+	return __reinsert_ablock(info, index, *block, b, root);
+}
+
 /*
  * Allocate an new array block, and fill it with some values.
  */
@@ -681,6 +695,72 @@ int dm_array_resize(struct dm_array_info *info, dm_block_t root,
 }
 EXPORT_SYMBOL_GPL(dm_array_resize);
 
+static int populate_ablock_with_values(struct dm_array_info *info, struct array_block *ab,
+				       value_fn fn, void *context, unsigned base, unsigned new_nr)
+{
+	int r;
+	unsigned i;
+	uint32_t nr_entries;
+	struct dm_btree_value_type *vt = &info->value_type;
+
+	BUG_ON(le32_to_cpu(ab->nr_entries));
+	BUG_ON(new_nr > le32_to_cpu(ab->max_entries));
+
+	nr_entries = le32_to_cpu(ab->nr_entries);
+	for (i = 0; i < new_nr; i++) {
+		r = fn(base + i, element_at(info, ab, i), context);
+		if (r)
+			return r;
+
+		if (vt->inc)
+			vt->inc(vt->context, element_at(info, ab, i));
+	}
+
+	ab->nr_entries = cpu_to_le32(new_nr);
+	return 0;
+}
+
+int dm_array_new(struct dm_array_info *info, dm_block_t *root,
+		 uint32_t size, value_fn fn, void *context)
+{
+	int r;
+	struct dm_block *block;
+	struct array_block *ab;
+	unsigned block_index, end_block, size_of_block, max_entries;
+
+	r = dm_array_empty(info, root);
+	if (r)
+		return r;
+
+	size_of_block = dm_bm_block_size(dm_tm_get_bm(info->btree_info.tm));
+	max_entries = calc_max_entries(info->value_type.size, size_of_block);
+	end_block = dm_div_up(size, max_entries);
+
+	for (block_index = 0; block_index != end_block; block_index++) {
+		r = alloc_ablock(info, size_of_block, max_entries, &block, &ab);
+		if (r)
+			break;
+
+		r = populate_ablock_with_values(info, ab, fn, context,
+						block_index * max_entries,
+						min(max_entries, size));
+		if (r) {
+			unlock_ablock(info, block);
+			break;
+		}
+
+		r = insert_ablock(info, block_index, block, root);
+		unlock_ablock(info, block);
+		if (r)
+			break;
+
+		size -= max_entries;
+	}
+
+	return r;
+}
+EXPORT_SYMBOL_GPL(dm_array_new);
+
 int dm_array_del(struct dm_array_info *info, dm_block_t root)
 {
 	return dm_btree_del(&info->btree_info, root);

drivers/md/persistent-data/dm-array.h

@@ -111,6 +111,25 @@ int dm_array_resize(struct dm_array_info *info, dm_block_t root,
 		    const void *value, dm_block_t *new_root)
 	__dm_written_to_disk(value);
 
+/*
+ * Creates a new array populated with values provided by a callback
+ * function.  This is more efficient than creating an empty array,
+ * resizing, and then setting values since that process incurs a lot of
+ * copying.
+ *
+ * Assumes 32bit values for now since it's only used by the cache hint
+ * array.
+ *
+ * info - describes the array
+ * root - the root block of the array on disk
+ * size - the number of entries in the array
+ * fn - the callback
+ * context - passed to the callback
+ */
+typedef int (*value_fn)(uint32_t index, void *value_le, void *context);
+int dm_array_new(struct dm_array_info *info, dm_block_t *root,
+		 uint32_t size, value_fn fn, void *context);
+
 /*
  * Frees a whole array.  The value_type's decrement operation will be called
  * for all values in the array