btrfs: remove ref_tree implementation from backref.c

Commit afce772e ("btrfs: fix check_shared for fiemap ioctl") added
the ref_tree code in backref.c to reduce backref searching for
shared extents under the FIEMAP ioctl. This code will not be
compatible with the upcoming rbtree changes for improved backref
searching, so this patch removes the ref_tree code.  The rbtree
changes will provide the equivalent functionality for FIEMAP.

The above commit also introduced transaction semantics around calls to
btrfs_check_shared() in order to accurately account for delayed refs.
This functionality needs to be retained, so a complete revert of the
above commit is not desirable. This patch therefore removes the
ref_tree portion of the commit as above, however it does not remove
the transaction portion.
Signed-off-by: Edmund Nadolski <enadolski@suse.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/backref.c

@@ -40,265 +40,6 @@ struct extent_inode_elem {
 	struct extent_inode_elem *next;
 };
 
-/*
- * ref_root is used as the root of the ref tree that hold a collection
- * of unique references.
- */
-struct ref_root {
-	struct rb_root rb_root;
-
-	/*
-	 * The unique_refs represents the number of ref_nodes with a positive
-	 * count stored in the tree. Even if a ref_node (the count is greater
-	 * than one) is added, the unique_refs will only increase by one.
-	 */
-	unsigned int unique_refs;
-};
-
-/* ref_node is used to store a unique reference to the ref tree. */
-struct ref_node {
-	struct rb_node rb_node;
-
-	/* For NORMAL_REF, otherwise all these fields should be set to 0 */
-	u64 root_id;
-	u64 object_id;
-	u64 offset;
-
-	/* For SHARED_REF, otherwise parent field should be set to 0 */
-	u64 parent;
-
-	/* Ref to the ref_mod of btrfs_delayed_ref_node */
-	int ref_mod;
-};
-
-/* Dynamically allocate and initialize a ref_root */
-static struct ref_root *ref_root_alloc(void)
-{
-	struct ref_root *ref_tree;
-
-	ref_tree = kmalloc(sizeof(*ref_tree), GFP_NOFS);
-	if (!ref_tree)
-		return NULL;
-
-	ref_tree->rb_root = RB_ROOT;
-	ref_tree->unique_refs = 0;
-
-	return ref_tree;
-}
-
-/* Free all nodes in the ref tree, and reinit ref_root */
-static void ref_root_fini(struct ref_root *ref_tree)
-{
-	struct ref_node *node;
-	struct rb_node *next;
-
-	while ((next = rb_first(&ref_tree->rb_root)) != NULL) {
-		node = rb_entry(next, struct ref_node, rb_node);
-		rb_erase(next, &ref_tree->rb_root);
-		kfree(node);
-	}
-
-	ref_tree->rb_root = RB_ROOT;
-	ref_tree->unique_refs = 0;
-}
-
-static void ref_root_free(struct ref_root *ref_tree)
-{
-	if (!ref_tree)
-		return;
-
-	ref_root_fini(ref_tree);
-	kfree(ref_tree);
-}
-
-/*
- * Compare ref_node with (root_id, object_id, offset, parent)
- *
- * The function compares two ref_node a and b. It returns an integer less
- * than, equal to, or greater than zero , respectively, to be less than, to
- * equal, or be greater than b.
- */
-static int ref_node_cmp(struct ref_node *a, struct ref_node *b)
-{
-	if (a->root_id < b->root_id)
-		return -1;
-	else if (a->root_id > b->root_id)
-		return 1;
-
-	if (a->object_id < b->object_id)
-		return -1;
-	else if (a->object_id > b->object_id)
-		return 1;
-
-	if (a->offset < b->offset)
-		return -1;
-	else if (a->offset > b->offset)
-		return 1;
-
-	if (a->parent < b->parent)
-		return -1;
-	else if (a->parent > b->parent)
-		return 1;
-
-	return 0;
-}
-
-/*
- * Search ref_node with (root_id, object_id, offset, parent) in the tree
- *
- * if found, the pointer of the ref_node will be returned;
- * if not found, NULL will be returned and pos will point to the rb_node for
- * insert, pos_parent will point to pos'parent for insert;
-*/
-static struct ref_node *__ref_tree_search(struct ref_root *ref_tree,
-					  struct rb_node ***pos,
-					  struct rb_node **pos_parent,
-					  u64 root_id, u64 object_id,
-					  u64 offset, u64 parent)
-{
-	struct ref_node *cur = NULL;
-	struct ref_node entry;
-	int ret;
-
-	entry.root_id = root_id;
-	entry.object_id = object_id;
-	entry.offset = offset;
-	entry.parent = parent;
-
-	*pos = &ref_tree->rb_root.rb_node;
-
-	while (**pos) {
-		*pos_parent = **pos;
-		cur = rb_entry(*pos_parent, struct ref_node, rb_node);
-
-		ret = ref_node_cmp(cur, &entry);
-		if (ret > 0)
-			*pos = &(**pos)->rb_left;
-		else if (ret < 0)
-			*pos = &(**pos)->rb_right;
-		else
-			return cur;
-	}
-
-	return NULL;
-}
-
-/*
- * Insert a ref_node to the ref tree
- * @pos used for specifiy the position to insert
- * @pos_parent for specifiy pos's parent
- *
- * success, return 0;
- * ref_node already exists, return -EEXIST;
-*/
-static int ref_tree_insert(struct ref_root *ref_tree, struct rb_node **pos,
-			   struct rb_node *pos_parent, struct ref_node *ins)
-{
-	struct rb_node **p = NULL;
-	struct rb_node *parent = NULL;
-	struct ref_node *cur = NULL;
-
-	if (!pos) {
-		cur = __ref_tree_search(ref_tree, &p, &parent, ins->root_id,
-					ins->object_id, ins->offset,
-					ins->parent);
-		if (cur)
-			return -EEXIST;
-	} else {
-		p = pos;
-		parent = pos_parent;
-	}
-
-	rb_link_node(&ins->rb_node, parent, p);
-	rb_insert_color(&ins->rb_node, &ref_tree->rb_root);
-
-	return 0;
-}
-
-/* Erase and free ref_node, caller should update ref_root->unique_refs */
-static void ref_tree_remove(struct ref_root *ref_tree, struct ref_node *node)
-{
-	rb_erase(&node->rb_node, &ref_tree->rb_root);
-	kfree(node);
-}
-
-/*
- * Update ref_root->unique_refs
- *
- * Call __ref_tree_search
- *	1. if ref_node doesn't exist, ref_tree_insert this node, and update
- *	ref_root->unique_refs:
- *		if ref_node->ref_mod > 0, ref_root->unique_refs++;
- *		if ref_node->ref_mod < 0, do noting;
- *
- *	2. if ref_node is found, then get origin ref_node->ref_mod, and update
- *	ref_node->ref_mod.
- *		if ref_node->ref_mod is equal to 0,then call ref_tree_remove
- *
- *		according to origin_mod and new_mod, update ref_root->items
- *		+----------------+--------------+-------------+
- *		|		 |new_count <= 0|new_count > 0|
- *		+----------------+--------------+-------------+
- *		|origin_count < 0|       0      |      1      |
- *		+----------------+--------------+-------------+
- *		|origin_count > 0|      -1      |      0      |
- *		+----------------+--------------+-------------+
- *
- * In case of allocation failure, -ENOMEM is returned and the ref_tree stays
- * unaltered.
- * Success, return 0
- */
-static int ref_tree_add(struct ref_root *ref_tree, u64 root_id, u64 object_id,
-			u64 offset, u64 parent, int count)
-{
-	struct ref_node *node = NULL;
-	struct rb_node **pos = NULL;
-	struct rb_node *pos_parent = NULL;
-	int origin_count;
-	int ret;
-
-	if (!count)
-		return 0;
-
-	node = __ref_tree_search(ref_tree, &pos, &pos_parent, root_id,
-				 object_id, offset, parent);
-	if (node == NULL) {
-		node = kmalloc(sizeof(*node), GFP_NOFS);
-		if (!node)
-			return -ENOMEM;
-
-		node->root_id = root_id;
-		node->object_id = object_id;
-		node->offset = offset;
-		node->parent = parent;
-		node->ref_mod = count;
-
-		ret = ref_tree_insert(ref_tree, pos, pos_parent, node);
-		ASSERT(!ret);
-		if (ret) {
-			kfree(node);
-			return ret;
-		}
-
-		ref_tree->unique_refs += node->ref_mod > 0 ? 1 : 0;
-
-		return 0;
-	}
-
-	origin_count = node->ref_mod;
-	node->ref_mod += count;
-
-	if (node->ref_mod > 0)
-		ref_tree->unique_refs += origin_count > 0 ? 0 : 1;
-	else if (node->ref_mod <= 0)
-		ref_tree->unique_refs += origin_count > 0 ? -1 : 0;
-
-	if (!node->ref_mod)
-		ref_tree_remove(ref_tree, node);
-
-	return 0;
-}
-
 static int check_extent_in_eb(const struct btrfs_key *key,
 			      const struct extent_buffer *eb,
 			      const struct btrfs_file_extent_item *fi,
@@ -964,7 +705,6 @@ static int add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
  */
 static int add_inline_refs(struct btrfs_path *path, u64 bytenr,
 			   int *info_level, struct list_head *prefs,
-			   struct ref_root *ref_tree,
 			   u64 *total_refs, u64 inum)
 {
 	int ret = 0;
@@ -1031,13 +771,6 @@ static int add_inline_refs(struct btrfs_path *path, u64 bytenr,
 			count = btrfs_shared_data_ref_count(leaf, sdref);
 			ret = add_prelim_ref(prefs, 0, NULL, 0, offset,
 					     bytenr, count, GFP_NOFS);
-			if (ref_tree) {
-				if (!ret)
-					ret = ref_tree_add(ref_tree, 0, 0, 0,
-							   bytenr, count);
-				if (!ret && ref_tree->unique_refs > 1)
-					ret = BACKREF_FOUND_SHARED;
-			}
 			break;
 		}
 		case BTRFS_TREE_BLOCK_REF_KEY:
@@ -1065,15 +798,6 @@ static int add_inline_refs(struct btrfs_path *path, u64 bytenr,
 			root = btrfs_extent_data_ref_root(leaf, dref);
 			ret = add_prelim_ref(prefs, root, &key, 0, 0,
 					     bytenr, count, GFP_NOFS);
-			if (ref_tree) {
-				if (!ret)
-					ret = ref_tree_add(ref_tree, root,
-							   key.objectid,
-							   key.offset, 0,
-							   count);
-				if (!ret && ref_tree->unique_refs > 1)
-					ret = BACKREF_FOUND_SHARED;
-			}
 			break;
 		}
 		default:
@@ -1092,8 +816,7 @@ static int add_inline_refs(struct btrfs_path *path, u64 bytenr,
  */
 static int add_keyed_refs(struct btrfs_fs_info *fs_info,
 			  struct btrfs_path *path, u64 bytenr,
-			  int info_level, struct list_head *prefs,
-			  struct ref_root *ref_tree, u64 inum)
+			  int info_level, struct list_head *prefs, u64 inum)
 {
 	struct btrfs_root *extent_root = fs_info->extent_root;
 	int ret;
@@ -1135,13 +858,6 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info,
 			count = btrfs_shared_data_ref_count(leaf, sdref);
 			ret = add_prelim_ref(prefs, 0, NULL, 0, key.offset,
 					     bytenr, count, GFP_NOFS);
-			if (ref_tree) {
-				if (!ret)
-					ret = ref_tree_add(ref_tree, 0, 0, 0,
-							   bytenr, count);
-				if (!ret && ref_tree->unique_refs > 1)
-					ret = BACKREF_FOUND_SHARED;
-			}
 			break;
 		}
 		case BTRFS_TREE_BLOCK_REF_KEY:
@@ -1170,15 +886,6 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info,
 			root = btrfs_extent_data_ref_root(leaf, dref);
 			ret = add_prelim_ref(prefs, root, &key, 0, 0,
 					     bytenr, count, GFP_NOFS);
-			if (ref_tree) {
-				if (!ret)
-					ret = ref_tree_add(ref_tree, root,
-							   key.objectid,
-							   key.offset, 0,
-							   count);
-				if (!ret && ref_tree->unique_refs > 1)
-					ret = BACKREF_FOUND_SHARED;
-			}
 			break;
 		}
 		default:
@@ -1205,16 +912,13 @@ static int add_keyed_refs(struct btrfs_fs_info *fs_info,
  * commit root.
  * The special case is for qgroup to search roots in commit_transaction().
  *
- * If check_shared is set to 1, any extent has more than one ref item, will
- * be returned BACKREF_FOUND_SHARED immediately.
- *
  * FIXME some caching might speed things up
  */
 static int find_parent_nodes(struct btrfs_trans_handle *trans,
 			     struct btrfs_fs_info *fs_info, u64 bytenr,
 			     u64 time_seq, struct ulist *refs,
 			     struct ulist *roots, const u64 *extent_item_pos,
-			     u64 root_objectid, u64 inum, int check_shared)
+			     u64 root_objectid, u64 inum)
 {
 	struct btrfs_key key;
 	struct btrfs_path *path;
@@ -1226,7 +930,6 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 	struct list_head prefs;
 	struct prelim_ref *ref;
 	struct extent_inode_elem *eie = NULL;
-	struct ref_root *ref_tree = NULL;
 	u64 total_refs = 0;
 
 	INIT_LIST_HEAD(&prefs);
@@ -1258,18 +961,6 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 again:
 	head = NULL;
 
-	if (check_shared) {
-		if (!ref_tree) {
-			ref_tree = ref_root_alloc();
-			if (!ref_tree) {
-				ret = -ENOMEM;
-				goto out;
-			}
-		} else {
-			ref_root_fini(ref_tree);
-		}
-	}
-
 	ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
 	if (ret < 0)
 		goto out;
@@ -1314,36 +1005,6 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 		} else {
 			spin_unlock(&delayed_refs->lock);
 		}
-
-		if (check_shared && !list_empty(&prefs_delayed)) {
-			/*
-			 * Add all delay_ref to the ref_tree and check if there
-			 * are multiple ref items added.
-			 */
-			list_for_each_entry(ref, &prefs_delayed, list) {
-				if (ref->key_for_search.type) {
-					ret = ref_tree_add(ref_tree,
-						ref->root_id,
-						ref->key_for_search.objectid,
-						ref->key_for_search.offset,
-						0, ref->count);
-					if (ret)
-						goto out;
-				} else {
-					ret = ref_tree_add(ref_tree, 0, 0, 0,
-						     ref->parent, ref->count);
-					if (ret)
-						goto out;
-				}
-
-			}
-
-			if (ref_tree->unique_refs > 1) {
-				ret = BACKREF_FOUND_SHARED;
-				goto out;
-			}
-
-		}
 	}
 
 	if (path->slots[0]) {
@@ -1358,12 +1019,11 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 		    (key.type == BTRFS_EXTENT_ITEM_KEY ||
 		     key.type == BTRFS_METADATA_ITEM_KEY)) {
 			ret = add_inline_refs(path, bytenr, &info_level,
-					      &prefs, ref_tree, &total_refs,
-					      inum);
+					      &prefs, &total_refs, inum);
 			if (ret)
 				goto out;
 			ret = add_keyed_refs(fs_info, path, bytenr, info_level,
-					     &prefs, ref_tree, inum);
+					     &prefs, inum);
 			if (ret)
 				goto out;
 		}
@@ -1447,7 +1107,6 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 
 out:
 	btrfs_free_path(path);
-	ref_root_free(ref_tree);
 	while (!list_empty(&prefs)) {
 		ref = list_first_entry(&prefs, struct prelim_ref, list);
 		list_del(&ref->list);
@@ -1502,7 +1161,7 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
 		return -ENOMEM;
 
 	ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
-				*leafs, NULL, extent_item_pos, 0, 0, 0);
+				*leafs, NULL, extent_item_pos, 0, 0);
 	if (ret < 0 && ret != -ENOENT) {
 		free_leaf_list(*leafs);
 		return ret;
@@ -1545,7 +1204,7 @@ static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
 	ULIST_ITER_INIT(&uiter);
 	while (1) {
 		ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
-					tmp, *roots, NULL, 0, 0, 0);
+					tmp, *roots, NULL, 0, 0);
 		if (ret < 0 && ret != -ENOENT) {
 			ulist_free(tmp);
 			ulist_free(*roots);
@@ -1621,7 +1280,7 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
 	ULIST_ITER_INIT(&uiter);
 	while (1) {
 		ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
-					roots, NULL, root->objectid, inum, 1);
+					roots, NULL, root->objectid, inum);
 		if (ret == BACKREF_FOUND_SHARED) {
 			/* this is the only condition under which we return 1 */
 			ret = 1;